Why do you call when you know you're beat???!!!

Quick update during my lunch break.  Last night, most of the time I knew when I was ahead, and I knew when I was behind.  I had AA four times and I think I started getting greedy.  The last time I had them I had only raised to $9 - I think I did that because the table was short handed during that time - usually it's good to raise to $12 or more with that kind of hand.  Anyway, the small blind snap called and the flop was Kh 9d 4h, he check called $18, and something told me STOOOPPPP he's got a set!... But no!  I decided to be stubborn and I tried to convince myself that he had AK (lol) and he was putting me on another bluff.... Earlier I got caught in a bluff but still won the pot because I had bet the winners off the hand and the guy chasing missed.  The turn was a blank, he checked I bet $43, and went all in and I gave the speech about him having a set and I called. I was right, he had a set,... I thought he had a set of 9's, I was wrong, he had Kings.  Ugggghhhh.  I couldn't put him on Kings, I would have expected a preflop reraise. 

So, how'd the bankroll go?... we'll I had started off good for a short time, and then was suddenly down about 90.  I had gotten back to 200 and staying right around that for about 1.5 hours and was thinking I was going to have an early night - I wasn't in the best of moods (HMM!  Go figure!)   I lost 200 in that hand... so I rebought for another 200 and things were going good, I got up to about 285, and then one person felted and he convince his friend to quit and it snowballed through two more people and basically broke the game.  Unfortunately, I got greedy and wanted to see if I could get it during the short handed game... two hands I had trips and lost to a boat, the case card in both situations.

Profit - None
Loss $200

I surrender!