Open, honest communication is mandatory. Gentleness is used as required, and roughness is used as mutually desired. The Rules Mutual consent for everything is mandatory. Remember, we are not using each other, we are loving each other. It is certainly all right for one partner to try things because the other person likes it even if they don't, but this is a gift freely given and cannot be required.
Great respect is mandatory.
Respect implies that you are aware of what the other person wants. You are willing to discover what they are capable of and what their sexual limits are. Your lover may have been injured psychologically or emotionally from past relationships. In fact this will almost certainly be the case, almost everyone has had their heart broken at least once. At the extreme, they may have experienced sexual abuse as a child.