I don't really know what to say. Where's the fun in a one night stand if it's only going to lead to heartache? That's stupid! If it's a one night stand you want, then don't even go there if you're in a relationship, no one deserves that. If you're single however, then you're free to do what you want. Don't act on your thoughts, unless you're single. It wont be harmless.
To love is to suffer. To avoid suffering, one must not love; but then one suffers from not loving. Therefore, to love is to suffer, not to love is to suffer, to suffer is to suffer. To be happy is to love; to be happy then is to suffer, but suffering makes one unhappy; therefore to be unhappy one must love or love to suffer or suffer from too much happiness. I hope you're getting this down.