Guilty or not Guilty?

Sex is a basic human need or not? With whom we can have sex or with whom it's going to be considered wrong? Is it necessary to have sex as a prime focus in order to continue a relationship? What's the psychology behind having a one night stand and a purely casual relationship?? Why it's so popular in today's times?? Why even there's is a need for such a system?? Why too much sex with your spouse after marriage or I a live in relationship can be a huge turn off or a disappointing factor for your spouse?? Let's explore these details in depth.