It's about being willing submit. I love feeling submissive, but it's a feeling I only ever had spasmodically until recently. I didn't know it was possible to have it as a (mostly) permanent feeling.
It wasn't because my husband wasn't assertive enough. He can, as I've said elsewhere, be assertive enough for ten, he just never went about it in the right way. It wasn't that he was unwilling to take the lead, just that I always resisted his attempts at leadership.
With me, the big difference was finding that he is able to control himself, and therefore can control me. Last night, for instance, in a tense PMT mood, I snarled at him about something, and waited for him to lose his temper and snarl back, thereby feeding my anger, as he would have done in the past.
Instead, he just looked at me, smiled slightly and said, “We'll talk about your little outburst later” (“talking” being a euphemism for him taking me out to his workshop and walloping the living daylights out of me). Instantly, my anger ebbed away to be replaced by that incredible mixture of anticipation, apprehension and arousal (the AAA effect), that I always feel in this situation.
It's not the threat of the spanking in itself that does it, though that of course is important, the major turn-on is the fact that with a word he can eliminate the anger and restore the ‘s’ feeling!