I think you're confusing "detachment" with the "cold shoulder".
You never have to act in a way you don't feel (i.e., if you don't feel like being kissed, you don't have to allow it). But there is nothing that says you can't accept a kiss if you want to. You can make yourself nuts analyzing his motives and trying to figure out how he will respond to how you behave. You can also easily slip into trying to control by withholding affection just to make a point.
If you feel like kissing, kiss. If you feel like having sex, have sex. If you don't, don't. If he asks why, you can tell him you don't feel like being kissed, or like having sex, without getting into a whole back-and-forth about it. If he starts blaming, you can say, "sorry you feel that way."