When you’re really happy, you’re rarely horny
You know how you’re horny when you’re sad? Well, during long stretches of time in your life when you haven’t had a major life dilemma, you haven’t had the urge to have sex at all. When you’re happy, you’d rather see friends, get out and see the world and do things outside of the bedroom. This could also be part of the way you’ve conditioned your brain. Your brain knows that it has to make the most of your happiness now, because once you’re upset again, it’ll be all sex all the time.