I'm sure this has been discussed in some detail in previous threads, but I'm new here and would like to get some opinions and advice here.

I'm finding myself getting busted on all-in situations with KK preflop.

I'm pretty good about multi-way craziness before the flop and getting away from them if I truly feel I'm up against AA. What I'm having difficulty with are the heads up situations where I end up going against AX and he spikes his Ace or something else gross. I also understand that this happens and it's just part of poker. My question is this?

Does it ever make sense to fold KK preflop if it's a large portion or all of your stack even though you're confident that you have the best of it and your opponent likely needs to spike his Ace or maybe flop a set?

If I could be 100% sure that he had a smaller pair then no worries, I'm calling every time. It's the situations where he is looking to catch an Ace that concern me more.

When is folding the right play if ever?