A while back I went in to donate blood, because I’m one of those disease-free, well-intentioned people the blood bank just can’t seem to get enough of. Also, I sort of enjoy it, because while I’m a sucker for attention of any kind, I’m not one of those people who enjoy manicures or spa treatments or other common forms of pampering. I’m really not so big on people touching me, is the thing. Hitting me, fine, I don’t mind that. But when a friend took me for a pedicure a few years ago, as a birthday gift, I just couldn’t shake the feeling that it was very, very wrong for someone else to be washing my feet. For money.

When I donate blood, I get to be the center of attention, but it’s altruistic, and I know my mother (an R.N. for over fifty years) would approve. The blood bank treats donors like royalty, handing out T-shirts and ice cream and all kinds of freebies if you’ll just open up a vein for them every three months. And you don’t have to worry about tipping anyone. It’s perfect.

Aside from the ice cream, the part of these visits I enjoy most is the pre-donation screening, where they take you into a small room and ask you about a hundred questions, to make sure your blood is market-quality. On this visit, a motherly-looking woman with a clipboard whips through the innocuous small-talk, like “Are you feeling well and healthy today?” “Are you at least 17 but no more than 60 years old?” and “Do you weigh at least 110 pounds?” (the blood bank is the only place I am ever asked this).

Things pick up pretty quickly after Round 1; soon we’re on to “Have you ever tested positive for HIV?” “Have you ever injected yourself with drugs or other substances not prescribed by a physician?” “Have you engaged in sex for drugs or money since 1977?” (not sure why that’s the cut-off, but no). “Have you been held in a correctional facility (including jails, prisons and/or detention centers) for more than 72 hours in the last 12 months?” “Were you born or have you lived in or had sex with anyone who lived in, or received blood products in, Cameroon, the Central African Republic, Chad, Congo, Equatorial Guinea, Gabon, Niger or Nigeria since 1977?”

It’s a mind-expanding interview, and I always find myself considering what an interesting life I might have led, had I made some different choices. Here I am, a lightly traveled, middle-aged lady with an eight-to-five job and two kids, but for all the blood bank knows I could have a prison record, a heroin habit, and a Gabonese lover. It’s something to think about. While I’ve never been much for risk-taking, it’s still nice that someone considers me capable of it. I feel oddly flattered, and then guilty. Maybe I should stop coming here, I think; it’s giving me ideas.

In fact I don’t donate blood as often as I should; the Q&A and the ice cream are fun but the physical experience can sometimes be unpleasant. The sudden drop in blood sugar always gets me, and I’ve learned that I have to drink the obligatory soda before they even put the needle in my arm. I’ve also learned to employ the same strategy I use for my stock market investments: Avert your eyes. But even with these precautions, I’ve had some bad experiences where I passed out, and a couple more where I’ve almost thrown up. I worry about someday hitting the rock-star trifecta—throw up, pass out, and die—even though I know the staff at the blood bank are trained to deal with exactly those kinds of events. That doesn’t mean they want to, and personally I wouldn’t blame them if they didn’t bother. After all, they invited me here specifically to give blood; I’m not allowed to just toss out whatever bodily fluids I please. Should I really expect them to deal with that kind of mess? I wouldn’t, if I were them. My blood isn’t worth that much trouble.

Blood’s a funny thing. Our bodies manufacture it readily, constantly. You can lose quite a bit and not suffer much harm. Yet the sight of it can cause pandemonium. Women—lucky us—get to deal with blood on a more regular basis than men, so you’d think we wouldn’t be as bothered by it. But seeing even a tiny bit of blood in the wrong context sets off system-wide alarms for every human. Bloodshed signals that your body’s integrity has been compromised; it indicates a hull breach, unauthorized access, a fence down somewhere on the South Forty. It means you’d better do something, and fast.

We see blood and we tend to panic, because unlike other bodily fluids, blood is expected to stay put. Our bodies have evolved features specifically for conveying other gunk in and out. Sweat, for example, doesn’t do any good inside your body; it has to come out to serve its purpose. Sweating doesn’t always make you feel better, but at least it’s supposed to. Sweating is good for your pores, whereas nobody makes the claim that bleeding is good for your veins. Sweat is unobtrusive, almost invisible. It doesn’t want to make trouble. “Don’t mind me,” it says as it goes about its business. “Just keeping the core temperature down; getting rid of some excess minerals. Nothing to worry about. Carry on.”

Whereas blood screams frantically and incoherently about your mortality.

Donating blood can be unpleasant, and bleeding from an accident or injury is no fun, but bleeding during a fight is scarier by several orders of magnitude. In that case, you’re bleeding because someone wants you to be, and you’ve got a lot more than mere physiology to worry about. This fact can really mess with your mind. In the boxing ring, for example, blood can change the whole tenor of a match. Some fighters get a boost in intensity from the sight of blood; others fall apart. Even though boxers rarely bleed enough to suffer serious harm, matches can be halted if there’s too much blood. That’s why a fighter’s cutman is one of the most important people in his corner. The cutman’s job is to stop the bleeding, fast, using ice, drugs, pressure—whatever it takes. A cutman strikes me as a very handy kind of friend to have.

I’ve never boxed, and my sparring injuries typically result in spectacular bruising rather than surface blood. But my first sensei did, one time, give me a fairly robust bloody nose. I didn’t notice the bleeding right away. I was mostly focusing on the pain, because getting hit in the nose is a complex sensation, comparable to the subtle notes of a fine wine. It hurts in a deep-set, headachy way, and it also stings, as if you’ve angered a tiny hive of bees you didn’t realize were living in there. After giving me a moment to savor this sensation, my teacher asked if I was OK, and I said I was, because I was still conscious. And then I looked down and saw blood on my gi. Not a whole lot, but a whole lot more than I should have been seeing. Before I could react, Sensei said something very typical of her, which means it was completely out of the blue: “You know,” she told me, “you’re with people who love you.”

Whereupon I burst into tears.

It’s kind of funny now, looking back on it. Seeing your own blood spread around like poster paint is a shocking experience. Fresh blood is so very red, so much more vibrant and alive-looking than anything else that leaks out of our bodies. Outside the bounds of our skin, it looks wrong, obscene, and unbearably precious. You’re seized with a desire to somehow pull it back into you where it belongs, maybe by inhaling really deeply. It’s like seeing your liver or kidney lying around on the bathroom counter. Hey, you realize; that’s mine. I need it back.

My instructor, who had dealt with a lot of bloody noses over the years, knew exactly what I was feeling. So she didn’t apologize, and she didn’t assure me that I was going to be all right. She didn’t even tell me not to bleed on the floor. Instead, she reminded me that I was safe. That I might be bleeding, but I wasn’t in danger of losing anything important: You’re with people who love you. It probably sounds a little weird, and borderline abusive, if you’ve never sparred. Hitting people you love is a peculiar pastime, and often a very unhealthy one. But sparring with the right people can teach you that even at your most vulnerable, you still have a lot going for you.

Years ago, when I was learning defenses against knife attacks in my first martial arts school, the instructor went off-script for a few minutes to explain some basic principles of knife fighting—which is quite different from disarming someone. If you’re in a knife fight, he told us, and you don’t want to kill your opponent, hold your free hand up in guard position and keep your knife hand behind you, so the weapon can’t be taken away. Only bring it out for brief slashing attacks across the arms, chest, face, and other places where you’re likely to draw blood quickly. “Show your attacker a lot of his own blood,” our instructor explained, “and he’ll go into shock.”

I’m always charmed by this kind of advice, which is simultaneously stone-cold practical and almost totally useless, like knowing you should make the sign of the cross if a vampire shows up. The fact is, I’m no more likely to get into a knife fight than I am to find romance in Gabon. But the strategy here is an appealing balance of the barbaric and the humane. Showing your attacker his or her own blood can end the conflict faster, and reduce the amount of damage. Without a cutman to stop the bleeding, the fight ends a lot sooner.

When my Sensei gave me a bloody nose, she didn’t try to stop the bleeding. She knew the more important task was to stop all the other things that leak out of a person when she sees her blood: Confidence, nerve, a healthy disregard for the constant closeness of our own death. You can’t staunch that loss with ice or pressure or Avitene. You have to remind the bleeder that the amount of blood she’s seeing is minuscule compared to all she’s got in her.

My blood is more mine than almost anything else I have. It’s produced by my body and vital to my existence. Which makes all the more remarkable this ability our bodies have, to spare something so precious, and just replace it, in the course of our ordinary lives. There’s very little else we can give of ourselves that is so important, yet so easily replaced. Except this: You can tell the people around you that they are loved, especially when you know they need to hear it. It may not get you a free pint of ice cream, but it’ll still make you feel good.