You really don't understand anything what TMZuk said, or just trolling?
If people are exposed to long term stress, looking for a way to vent the stress. There are many ways to do something like this: Alcohol, tobacco, coffee, drugs, sex etc.
Sex is one of the most reliable ways to do it and If it's sex with someone you love, the effect is much greater. Moreover, If it is with the person you really love, sex may not even be necessary. Even small things (holding hands, hugging, kissing, sleeping in the same bed / tent) help a lot.