How can I help control myself???

[skiier04]

Okay well I'm a winning small stakes player with only around a $350 bankroll. I mainly play $10 SNG's or >$5 MTT's. The problem I've been having is occasionally when I suffer a tough beat, or just for the hell of it, go way over my limit and play something like a $50 or $100 heads up match or $50 SNG. I've been lucky so far, as I've been able to place/win many of my high stakes excursions. I know this luck will not hold up though, as I am almost positive I am nowhere near as good as the players at those limits. What can I do to stop myself from doing this in the future, because if I dont, I fear my bankroll will be in serious jeopardy. Thanks in advance.