It is thought that there is a set point for happiness. It's in our genes. This counts for 50% of our happiness.
The other way to be happy is to do things that create happiness. Taking vacations, reading, spending time at the computer, being with friends, and especially being with a spouse that is also your best friend. I'm lucky that way, my wife is my best friend and also my sex partner.
Golf makes me happy.
Sex and happiness. How can sex not bring happiness? Wouldn't it be cool to invent a pill that would create a 1 hour orgasm? Wow. Talk about not needing recreational drugs anymore. Man o man.
Sex has got to feel good, because if it didn't, we would not do it and our species wouldn't survive. So I'm all for a surviving species, so come on baby, let's spread some seed.