Turning forty was the Big Event of my week (though Brazil’s poor performance in the World Cup semifinal gave it a run for the title of B.E.–what happened?!). Our forties might be the adolescence for our second half of life—we’re not yet considered old but certainly can no longer claim to be young.

I’m fascinated by how simply aging gives us a new perspective without our having to work at it, a concept that didn’t occur to me in my twenties and early thirties. I’ve noticed a few contributing factors.

There is, of course, the physical side. I had the good fortune to spend some time with a friend’s two-year-old recently. I still enjoy climbing on jungle gyms and blowing bubbles, but the pulled calf muscle that’s been hanging on for months was easily be tweaked by a race across the playground—a race with a two-year-old, remember.

As I’ve aged, my relationship to time has changed. Ten or fifteen years in the future is now imaginable. As recently as a few years ago, I knew I would probably exist in ten years, but I couldn’t hold onto any idea of myself or my life that far away. Now, my friends and I wonder whether we will still own our houses when our fifteen year mortgages are paid off. The prospect is terrifying but comprehensible.

I am also occasionally more at ease within my life. I feel as if I am just beginning to see that much of what I worry about isn’t worth worrying about but am not yet old enough to actually stop worrying about it. I suspect this comes from failing and realizing that the world didn’t cease to exist, though I am still too often convinced that it will after my next horrific mistake.

All this makes it easy for me to understand why people go out and buy sportscars in their middle age. Because what we use to define ourselves—the goals, the accomplishments, the roles we play—and their meanings get a bit slippery. Sports cars are solid.

I get the sense, though, that if I can stick with the slipperiness, something interesting is waiting around the bend. I’ll keep you posted.