"The Best Form of Foreplay
I'm not sure where I came across the phrase, but I think it embodies an important point. Most talk about sex in our society assumes the context of seduction, one night stands, affairs, short term relationships of one sort or another. Much, I suspect most, sex actually occurs in long term relationships, marriage or the near equivalent.
I gather that a lot of writing about how to make a flagging marriage work takes it for granted that the objective is to get back to the intense feelings of courtship, to "rekindle the passion." I doubt it works. A long married couple that wants to recapture the intense emotions of their courtship would be better advised to have children; they will discover that the parental focus on a child has the same intensity, the same insane illusion that the object of love, this time parental rather than erotic, is the most important being in the universe.
In a long term relationship, success has more to do with love, less to do with lust—which is not to say that the two do not correlate. Doing something for your spouse that she (or he) would otherwise have to do for her (or him) self is one way of encouraging it.
(Thoughts in part provoked by a silly and self-indulgent article in the Atlantic whose author, having had an affair and ended a long-term marriage, was moved not to apologize to husband and children but to pontificate in satirical mode on the problems of modern marriage.)