sticking to religious standpoint, which is the only one that matters, says... sex outside of marriage is wrong. it's a sin and sin pushes us away from God which is obviously a bad thing as that can lead you to hell.

but us human's, given our fallen nature(which has always been that way since the fall of Adam/Eve), tend to find bad things appealing as they seem harmless to us and the sexual drive is the easiest thing to exploit since it's so appealing. but damages your eternal soul and can possibly lead you to hell.

praying often (preferably The Holy Rosary daily(i am a Catholic)) gives you strength, over a period of time, to resist your natural sexual urge (trying to resist that by yourself is not happening). just trust me on that. many people around here will likely see this and laugh though since they don't believe in God.