On that which doesn't kill one making one stronger

I don't remember precisely when I first heard the adage that "Whatever doesn't kill you makes you stronger," but I'm pretty sure it was sometime in high school, and quite possibly in a quarter-long class I took my sophomore year called, no joke, "Keys To Success." At the time, the saying seemed logical and fortifying; after all, I'm all for getting stronger. These days, however, I have my doubts.

First, the saying seems to exist in the present tense, but in theory it's drawing from the past and in practice is predicting the future. That is, it seems to be claiming that "Whatever isn't killing you is making you stronger," but in practice more likely means "Whatever didn't kill you in the past made you better able to deal with things that are now trying to kill you, so chances are good that you'll be able to deal with them in the future." I don't really disagree with that sentiment--but neither does it seem to advocate embracing the things that could likely kill you, the way the original does: "if it's not killing you, it must be making you stronger!"

The problem is, of course, that sometimes whatever it is it might just be killing you. And how is one to know the difference?

I've trained for and run three marathons. I've moved myself across the country at least three times, to places where I hardly knew anyone. I've finished an MA and am working on a PhD. I've commuted on my bicycle, even in the snow, for five winters. And I've recently become a hard-bitten Mouse Wars veteran. None of these things has killed me (yet), and ostensibly all have made me stronger.

But I have a tibial stress fracture. I live far from my oldest friends and my family. I have the wrinkles to show for my graduate work--and maybe my cold-weather biking! My heart has grown that much icier, creating and disposing of mouse corpses. Am I better off being "stronger"?

There's a U2 song that includes the lines "some things you shouldn't get too good at/like laughing, crying, and celebrity." Killing mice, knocking out papers in the early hours of the morning, convincing oneself it's a good idea to run 15+ miles on weekend mornings or surf one's bike through snowdrifts, and moving away from places one has learned to call home are probably things one shouldn't get too good at.

And what about having one's heart broken? If it doesn't kill one, it must be making one stronger, right? Or is it another of those things one shouldn't get too good at, because it does end in killing one a little bit--and without the advantages of fabulous abs and quads, or mad mouse-disposal skills?

So if one is not trying new things based on the hopes that if one survives them, one will be stronger, what should be the motivation for adventure and productivity? For a few years, I've been trying out the philosophy that simply being afraid of something is not, by itself, a good enough reason not to do it. And then there's Rilke: "But those tasks that have been entrusted to us are difficult; almost everything serious is difficult; and everything is serious." The serious things are worth doing anyway.

Life is killing all of us, but I guess that shouldn't stop us from getting as much as possible out of it first--stronger or not.