Laying down KK post-flop is something you have to be able to do, even if there is no ace on the board. On an ace flop, it should be very standard.. although I'm not saying you should necessarily give up on the pot if there is an ace, but you get the point.

Preflop is a whole different story. It is often correct to fold QQ and AK preflop, KK is highly debatable. There are countless threads on FTR alone that discuss whether it is correct to sometimes fold KK in fear of AA preflop. I won't even go there because that discussion has worn me out. From what I have read of your posts, you don't seem like a very experienced player.. pay off AA when you have KK, very simple.