Dopamine, serotonin, oxytocin and endorphins are the quartet responsible for our happiness. Many events can trigger these neurotransmitters, but rather than being in the passenger seat, there are ways we can intentionally cause them to flow.
Why are heterosexual men so fascinated by women's breasts that we sometimes act as if the breasts are the seat of the soul?
If you're having sex outside committed relationships, you will have to stop. Why? Because past a certain age, casual sex is like recreational heroin -- it doesn't stay recreational for long.