when can i make a laydown like this??

[DcifrThs]

Well actually, i'd like 2 of them but only 1 id call a "legitimate" laydown.

playing party 30/60. great fishy limps, i iso-raise KQo pretty early (UTG+2). flop comes Ks7c3h. he bets i raise he calls.

turn blanks off. same action.

river comes Jd. he bets. i want to fold KNOWING he has KJo without a question in my mind (hed raise it if it were suited). but i call and lo and behold. KJo...enon told me i should feel great about it and make it 100% of the time. i agreed of course so thats notthe real one...but still "coulda" folded.

HERE's the real laydown i wanted to make.

stars 30/60 game. 1 limper, 1 raiser, 1 3bettor (no info except 3bettor is a little loose aggro). i cap with AsAc. loose bb calls 3 cold all call.

flop comes Ks5cXx. checked to limper who bets, raiser calls 3bettor raises i 3bet. flop bettor and raiser call.

3 to the turn. 7c. checked to me i bet 1 caller and now the flop raiser checkraises. i look at the board, look at the action and say, "hes got AcKc" and 3bet, both call.

river comes 3c or some low club. check, AcKc guy bets and i really want to fold. i know im beat here. and i mean flush vs. pair beat. but i look at the pot (1377), look at the size of the bet ($60). and i think about enon and how i say to him "yea i make mistakes, but i almost never make pot costing ones" and i call.

comments...when, if ever, can i fold on the river if i KNOW im beat?

-Barron