Using GSS data, here's the average number of days in the past week that people felt "excited" or "overjoyed" as a function of their age (grouped into three-year bins):
Everyone's more likely to feel excited than overjoyed, perhaps because overjoyed implies that the thing you were excited about actually worked out the way you'd hoped. Age is not correlated with feeling excited -- good news -- but it is with feeling overjoyed. * It declines from the late teens to the early 40s and levels off afterward.
This pattern serves young males because it builds team spirit among their coalition of desperate risk-takers, which older independent males don't have to worry about as much. And it serves young females because it makes them cute. When was the last time you saw a 30 year-old woman give a guy one of those run-jump-hug thingies?
When I'm 50, I hope I'll be self-deluded enough to say things like, "Well, I've been there and done that, and I don't need a girl who's overjoyed so often -- too much drama. I need someone who's calm and still." Probably I won't be, if my current inability to repress ugly facts is any guide.
Middle-aged guys get fired up themselves when they're coaching a winning team, as they watch their junior foot soldiers overwhelmed with emotion. And what father doesn't light up inside when his daughter is on cloud nine and runs up to give him one of those "Daddy!!!!" hugs for no apparent reason? Obviously we continue to value this trait in our close friends and family members as we age.
The only reason we say at that age that we don't want a romantic partner who's easily overjoyed is that for most of us, that type of partner -- namely, a young one -- couldn't be farther out of our league. It's better for the ego then to make believe that it's not what we really value and just get on with life. (See this related post on how guys' attitudes toward girls change over the lifespan.)
Since your own level of joy will probably hit bottom around age 40, you'd better have an outside source to give you a daily shot in the arm, probably from interacting with young people. Hopefully that means you'll have a 20 year-old wife. But even if not, working with young guys and especially young girls should do the trick. (One of the few fringe benefits of teaching.) And then there's having kids of your own -- although they're not exactly going to be a reliable source of joy in your life until they leave for college, those exceptional moments aside.
As for 40+ women, don't do this. Working with high school or college girls every day will just depress you as you become unable to block out how pretty you used to look when you were their age. And the young guys will mindlessly blurt out something about you being old, or make you the object of their fantasy where you'll be an easy lay, unlike the girls with annoying high standards their own age. There's always the religious life -- many middle-aged women seem to get a lot emotionally out of that, rather than going to church just because they have to.
I wonder if that's why Jesus is so much more popular than other central Christian figures -- having died relatively young, he can't be imagined as an aging man. Women can view him either as their surrogate son or as the not-too-young rockstar whose undivided attention will make them feel young and special again.
Look at any painting of Saint Paul, though, who lived into his 60s -- he always has either a widow's peak or a bald head, a wrinkled face, and other signs of age. Not the joy-spreading performer type who women will naturally turn to in order to feel younger and fulfilled. Some psychologist must have studied the frequency of women having erotic dreams about Jesus vs. other important Biblical figures.
I'm sure this is why flaky Gaia worship will never convert more than a tiny percent of middle-aged women: there's no younger dude to look upon and speak to you.
Whatever you turn to, plan ahead so you can ease into it gradually. Born-agains and the creepy old guy in the club appear more unhinged than their same-age counterparts who've been at it for awhile.
* Pearson correlation is -0.58, two-tailed p = 0.012.
GSS variables: EXCITED, OVRJOYED, AGE