Everybody I know who turned 50 had a weird existential crisis about not having lived the life they thought they should. Looking at my life right now, I'm not where I thought I'd be at 40, but I certainly don't look back with a whole lot of regret. I've had a pretty good life so far. I've done a lot of cool things with a lot of cool people. I've had little heartbreak and lots of good fortune. I've made the wrong choices for the right reasons, and done the right things when it felt all wrong.
If the second half of my life is half as good the first, I'll be all right.