When you are having great sex it is hard to leave cause you keep wanting more. I think the best thing is to have great sex with someone your love and who returns that love. Honestly as a man who can control my emotionss i might stay in a relationship with great sex but only if i was sure i would not hurt the person, cause sometimes great sex can make women fall in love (men too). If you want to have more with this person then you need to find out how the other person feels maybe all they want it great sex and the only choice you have is to either get out of the relationship cause there is no future or stay in if you can control your emotions.