I posted this in my thread on MTT time management, but I think it fits your topic...

Classic exhaustion example...2 nights ago, [now a few weeks]
I was pretty well ahead[MTT], and got into a (stupid) hand with A8s...
I raise up, 1 caller, the flop comes QKK. I check, He checks...
Turn Q. I check, he checks,
River 4 (no flush draw on the table)...
So I figure he's got a mid pp and I am looking at a dead board with my ace kicker... I bet. He raises. I think ??44?? It was a 4? nah... So I call... He flips 88, I think AHA!!! I outkicked you for the board with my stupid A...
LOL... wait a minute... why are the chips sliding towards him? There's no such thing as 3 pair, I clearly have him out-kicked...

Then I look at the board again... It wasn't QKKQ4... it was QKQQ4...
I am a tired donkey - and he has a full house (and I KNEW he had a pair 77-TT!)