Sometime during the past year I became persuaded, unwillingly, that a truth I had darkly suspected for some time about myself was actually true: I am not, and presumably men in general are not, actually monogamous by nature. If we appear to be monogamous it is a secondary emotion, a consequence of empathy for and desire to avoid causing pain to our partners--a logical and not an emotional choice--but our basic nature is to treat relationships on an individual basis: I can be completely and totally in love with Sarah and it has nothing to do with anyone except Sarah, and I can at the same time be mildly attracted to Sue because of who she is, and at the same time I can admire, respect, and love Sally on her own merits. These feelings are not mutually exclusive except to the extent that, for instance, Sarah and Sally each feel threatened by my feelings for the other, in which case circumstances force me to choose between them. Part of love is wanting what makes the other person happy, and so obviously if Sarah is unhappy if I love Sally and vice versa, loving both is an inconsistent state of affairs and can't actually exist for long. In practice, here in the mortal realm the choice is simplified by the temporal ordering: typically you'll find that I've made a commitment to Sally prior to ever meeting Sarah (e.g. we're married) so the relationship with Sally takes precedence.
Of course, this propensity to treat relationships individually doesn't always relate to marriage. You'll see it crop up in other places, such as dealing with children (fact: you don't have the same relationship with all your children, and with some you get along better than others). You'll also note that Heavenly Father is renowned for his ability to have personalized, completely individual relationships with all of his children... and Heavenly Father is male. Significant? I don't know, maybe all celestial beings are like that.
As always, I may be completely wrong about this whole topic, but this is my best understanding from the data that I have available to me here and the thinking I've been able to do. If I'm wrong it will be pointed out to me eventually by someone or other or something.
 To pick a name out of a hat.
Rock Is Dead. Long Live Scissors!
"The presentation or 'gift' of the Holy Ghost simply confers upon a man the right to receive at any time, when he is worthy of it and desires it, the power and light of truth of the Holy Ghost, although he may often be left to his own spirit and judgment." --Joseph F. Smith (manual, p. 69)