Hmm. Well, if you're planning to have kids, I'd really recommend doing that before forty, so you have a fighting chance of seeing grandkids grow up. Ever wanted to climb a mountain, run a marathon or play a social team sport? Not that many people can't do these things when they're older, but what you don't see are all the ones who can't because of chronic injuries (he says, from the sidelines, as he contemplates never playing soccer again). I'd also say "learn to make friends out of strangers", because of all the older people I know, it's the ones who have the most friends who are the happiest.