There are seldom any real consequences. But anyone who expects real life to be that way is in for a big surprise. The only kind of sex that has no serious consequences is masturbation. There's a difference between sexual desire and love. Sexual desire is a powerful physical excitement.
Love is a powerful caring for someone else.
It can also be physically exciting. Love can exist without sexual desire, and sexual desire can exist without love. Many people are happiest when both love and sexual desire are shared by both partners. Having sex with another person is very personal and very intimate. No matter how brief, sexual relationships are partnerships.