I found this passage that I wrote down months ago on a slip of paper while finally clearing the clutter near my computer. Doesn't matter, though, because it's timeless.
This is from Martin Seligman's book, Authentic Happiness.
"If you want to be happy
for an hour, take a nap
for a day, go fishing
for a month, get married
for a year, get an inheritance
for a lifetime, help someone"
What more is there to say?