JJ, I think both of your assessments of why the "HD" partner might get miffed when the other partner becomes more sexual are absolutely correct. And I'd like to throw in another one: both partners have sort of defined the sexual "zone" as the HD's territory. When the LD partner starts to initiate (in the HD's opinion) TOO MUCH, it's as if the LD is getting in on the driver's side when up to now both have agreed that the LD belongs on the passenger side. I think sometimes when the HD says they want the other to be more sexual, what they really mean is that they want the LD to be a more active passenger. They don't want the LD to take over driving, buy a new car, have the old one painted, etc. It definitely upsets the balance of power.
BTW, it feels more to me like this is true in M's where the H is the HD. I don't know if it would apply to your sitch or not. What do you think?
