On Sunday, I celebrated my 50th birthday by going fishing.

It was a cold and windy day on the river and the fishing was terribly slow, which afforded me far too much uninterrupted reverie about those big themes of life that such a momentous birthday as the 50th seems to spark in people. For three hours or so I stood in icy water to my waist, alone, flailing away in utter futility at an elusive prize I had no hope of landing. My lower body was thoroughly numb, my nose was leaking, and my joints had become so stiff that I could hardly walk without risking bodily injury.

Perhaps it was the hypothermia at work, but at that moment my little birthday fishing trip suddenly seemed a perfect metaphor for the ravages of having lived half a century. It was a disturbing thought, so I hobbled out of the water as fast as my seized-up body would allow and sat on a warm rock until I felt closer to 49 again.

I’ve decided it’s better not to think too hard about turning 50. It’s just something that happens, after all, so it’s probably better to dwell on the fact that the only alternative to reaching 50 one day is to die before you get there. And that’s not really much of an option, when you think about it.

I read somewhere that on Jan. 1, 1996, the very first baby boomer in the country turned 50. Since then, 11,000 boomers a day have been turning 50, or one every 71/2 seconds. This explosion in membership in the half-century club has, of course, spawned countless books by 50-something pop psychologists that attempt to massage the collective ego of all those millions of boomers who can’t bear the thought of getting old.

These are the books that allow your average 50-year-old to conveniently forget that Mozart was dead by 50, that Henry Ford had already invented the assembly line by 50, that Darwin had written “The Origin of Species” by 50, that John Updike already had a Pulitzer under his belt by 50 and that John Kennedy was elected president four years before he turned 50.

Instead, the books purport to make turning 50 into a time of joyous celebration rather than a dreaded transition. They use terms such as “renewal,” and “rebirth” and even “midessence,” whatever that means. Don’t worry about all that you have not accomplished, the books urge us, but think instead of all the great things you have left to achieve.

Personally, I prefer to console myself about this aging business with a far more modest yardstick:

People haven’t begun to call me “Grandpa” yet, at least not to my face.

I don’t grunt yet when I put on my socks in the morning, and usually can match them fairly well without assistance.

I don’t drool, except maybe when I’m sleeping.

I still have almost all of my teeth, if you count the two new ones I bought from my dentist recently, and can walk up a whole flight of stairs without taking a rest.

So far I am still able to eat pizza and Mexican food late at night without stomach trouble.

I’ve had gray hair since my late 20s, so the new ones to come won’t upset me.

Hair has not yet begun to sprout in tufts from my ears or my nose.

Not only can I make it through David Letterman, but I’m able to catch at least half of Conan O’Brien’s show before I begin snoring away on the couch.

I almost always remember to zip up my fly, and so far have never once forgotten to zip it down when necessary.

I fully intend to feel like 30 forever, or at least until my AARP card and that first issue of Modern Maturity magazine arrive in the mail to tell me differently.