Having sex is a personal choice either for pure physical pleasure or as another form of exercise.It is a very natural urge as God has made us like that.Some want it very badly but can't find a mature woman.Others go for it and do find one.On the whole,the most vital guideline should be to have SAFE sex with MUTUAL CONSENT.Of course it should be an enjoying experience.No one should feel guilty after the same as it is VERY,VERY natural to feel attraction for members of the opposite sex.