There's an ongoing debate between two false views. Some Christians think love is a command (after all the two great commandments are to love God and to love others) and therefore doesn't involve feelings. The other view is that love is obviously a feeling and thus isn't really something we can be responsible for. We can't be commanded to love if it's something that happens to us, as feelings do. On the latter view, those who fall in love are just lucky, and there's no room for choosing to love someone. On the former view, as long as you do the right actions you're loving, and it doesn't matter if you feel the right feelings.
I've resisted both views before. See the comments on my Christian Hedonism post from a few years ago and Wink's Love is not a Choice post from a couple months later. (By the way, I'm not saying Wink commits one of the two errors, His denial of love as a choice isn't to remove ourselves from being responsible for our feelings. Rather, the reverse -- he sees love as involving feelings that we're obligated to feel.)
I've been reading a commentary on Proverbs, and I came to Proverbs 5 last week. It struck me as a particularly nice example of what I said in those comment sections. In this passage, it's even stronger in one sense. It isn't just love that's commanded here. It's utter delight and intoxication, the height of positive emotional responses. It's so clearly a feeling that I don't know how anyone could try to claim otherwise. Yet it's also so obviously a command in context that it would take extracting the passage from its literary surroundings and reading the grammar extremely woodenly to deny that..
Drink water from your own cistern,
flowing water from your own well.
Should your springs be scattered abroad,
streams of water in the streets?
Let them be for yourself alone,
and not for strangers with you.
Let your fountain be blessed,
and rejoice in the wife of your youth,
a lovely deer, a graceful doe.
Let her breasts fill you at all times with delight;
be intoxicated always in her love.
Why should you be intoxicated, my son, with a forbidden woman
and embrace the bosom of an adulteress? [Proverbs 5:15-20, ESV]
It is technically true that some of the verbs are not grammatically commands but are actually blessing formulas (often translated in other translations as "may you be..."), but in context the entire section is contrasted with getting tangled up in adultery, which the father commands the son to avoid. Part of the remedy for the son's temptation toward adultery is to take delight in his wife. It has the force of a command even when it technically invokes a divine blessing to provide this for the son. In other words, it's a lot like many passages throughout the Bible that assume full human participation and moral responsibility in living the righteous life despite the need for God to provide grace to enable the righteous to be righteous.
Compatibilism about divine sovereignty and human responsibility explains how the two seemingly opposed theses can both be true and both be affirmed throughout the Bible (often in the same passages). So those who want to reduce everything to one of the two elements (divine sovereignty or human responsibility) need to force these texts into one of the two errors above. But that's not necessary. The command to love God and one's neighbor requires both divine sovereignty in enabling us to feel that love and human responsibility so that we can be accountable for having that emotional response. This passage illustrates that the same is true of sexual enjoyment, and I think in context it must apply to delighting in one's spouse sexually when that spouse is old and gray and not delighting in anyone else in the same sense, even if the feelings and attraction one feels naturally go in the opposite direction.
My wife isn't old and gray yet, but assuming a natural lifespan she will be one day (and she thinks she's earned a few gray hairs already). If I ever get to the point where I'm not intoxicated by her sexually, something is missing in my inner life. I'm morally deficient if I can't focus my sexual delight on my wife to the point of being intoxicated by her. I'm even morally deficient if I focus it on anyone else, even if I also focus it on her. [I'll leave aside cases when there's no sexual drive at all, at least in cases where there's no temptation to adultery on the part of either spouse. My point here is that sexual desire on the part of either spouse requires at least some level of commanded delight in the other spouse to the extent possible. Even a low sex drive is compatible with enjoying sex, even if there's a reduced desire to initiate it. Delight in the other's delight is a kind of delight, and many cases of lowered sexual drive allow more enjoyment than that.]