Respect for yourself, respect for others and respect for your culture. So, respect, basically.

We live in a culture where serial monogamy is the norm. Virtually every person you hook up with will expect an exclusive relationship to provide some security and stability, until things change. The ideal is for life, but that doesn't happen as much now. Sure, there are people who are happily polygamous or polyandrous, but they are vanishingly rare, in the Western world at least. Being part of this culture, you have to respect the expectations of the people you hook up with.

Many people feel guilty about dogging around behind their partners back, and not just because if they get caught there will be trouble. It is disrespecting the person you are with. Saying, in the most cowardly way possible, that they are not good enough for you all the time. Tearing down someone you are supposed to have feelings for. The few guys I know (please note, I did not say friends) who cheat pretty much constantly don't give a crap about anyone at all including themselves, never mind their frequently changing partners.

And finally, self respect. Basically, "I gave my word and I will bloody well keep it." To most people, that is important, seeing as keeping your word is the basis of civilisation.

Thank you! You have just given me a right old headache to try to explain this!