I really am supposed to go broke

[Bet-and-win88]

I just played my usual NL ring game online (I don't like online poker because my edge of reading my oppenents drops down).
Stacks both about 200
I get dealt KK UTG+1 9 handed, blinds 1/2 and see UTG limping. I make it 12 (pretty loose callers out there and this raise is necessary to get heads-up), 3 folds and MP (don't know the exact position) calls without any hesitation. My read was that he played his big hands preflop slow. I've played tight so far and only raised with premium hands and I think you knew that. So this instant call made me suspicious. Wouldn't he reraise with JJ, QQ, AK to isolate me? Everybody folds except the BB.
Flop: 555
BB checks and I make it 35, MP calls instantly, BB folds.
And at this point I was pretty sure he got aces out there. He would have reraised his high pairs and broadways except AA (and KK) and he wouldn't call an almost pot-sized bet with two overcards or a middle pair.
I check the turn, he checks behind.
I check the river, he checks behind and shows Aces.
(strange check there)

I don't want to analyze it any further but I'm pretty sure, that I have some problems with my gut instinct. Everybody is supposed to go broke on that hand but not me. It isn't my weak-tight attitude because I can play very aggressively when necessary.

I had always a very good gut instinct and it was rarely wrong, but in these situations I can't decide whether I'm blessed or cursed.