Recently played Cash game $2/$5. Was doing pretty well up $150(total BR $450) when I get dealt AA(diamond,club) on the button. Four players limp, I raise to 4 big blinds($20), 3 players call one folds - so 4 players see flop, me included(multipot). Flop comes 8,9,J all Spades. Everyone checks, I make $30 CB, 2 players fold - the CO calls. Turn is 7 clubs - CO checks....I check as well(didn't want to throw 2nd barrel w no outs on a coord board). River is A(hearts) so i make a set. CO makes $70 bet. My thinking process is my set is BEHIND since I made my CB based on position, checked turn, BUT because I don't have 12+ outs on the turn - I fold on river bet. He SHOWS me KQ (Q a spade) and I kill myself. I thought I played this well, but maybe missed some details leading up to the river?