let's start with this fact: round things are fun. compare peas, for example, with broccoli. other fun foods: m&m's, isreali cous cous, and papaya seeds. well, i guess you don't actually eat papaya seeds, but they look like rabbit poops, and that makes them hilarious.
who doesn't have fond memories of an older sister standing on your head in a netted playpen full of large primary-color pellets while your parents ignore your anguished shrieks and drink beer by the pitcher? no? well-- i feel sorry for you, then. but those of us who are blessed with those memories have to nod our heads in agreement and say, yes, those ball pits are sound evidence that round things are fun (...wait-- maybe it was me standing on my sister's head? yes, that would make more sense...fun!).
how about when you saw a bean bag chair ripped open for the first time? don't lie and say it was anything less than a delight.
snow balls. gumballs. baseballs. giving someone blue balls. good times! breasts are round, and they are fun. balls we've already mentioned, but some people even think they are fun without turning them blue (and to those people who think breasts are the most fun, and to those who think balls are the most fun: you're both right! round things are fun).
anyway, this not even remotely comprehensive list of evidence is to remind you: there is a curvature to happiness.
so, how can this be applied? i'm not sure. but the shape of happiness is a fact we just proved.