Help - No lack of skill, but lack of willpower

[kismet]

I've come to a very bad realization. I have never cashed out of our local bar unless it was because the game is breaking up. I can't seem to quit no matter if the game is good or bad. Tonight I played my best, and was reading hands perfect. I tripled up my $40 buy-in in about two hours. The fish were pretty much already broke at this point, and then something familiar happened. I looked down at my stack and said ok I'll just wait till they bust out then cash out for a profit and go home early. Not two hands later I took a horrible beat from a good player for about $25. I stopped thinking of cashing out and before I knew it I was broke. AGAIN. The last 4 nights, and many many other times I have said to myself, finally I played well and I'll end a winner.. then go broke. Instead of up $350 for the last 4 nights I am now down about $120 just because I don't quit when I think I should quit. I realized tonight I do this far to often, and would probably have a super bankroll right now if I didn't have to play till close every night. Mostly because I enjoy the game and beating every dollar out of a table. What can I do? It is easy to tell myself at home, ok I'm gonna cash a profit tonight, but it never works. It is always just one more loop, or till the fish bust out, then somehow I rack off all my money before I realized what happened. I'll be off tilt again tommorrow and ready to play my best again. Maybe I can stop ahead... Maybe...