Stopping Daytrading

Well, that didn't last long. I think it is definitely possible to make money using this daytrading method, but it is definitely not for me. The problem is that though entry to positions is "automated" the exit is discretionary. If you say it is the end of the session, then you can't do it exactly at the end  -say at 4:30pm for the ASX200 futures. So, do you do it at 4:00 pm? 4:10pm? 4:30pm?, 5:10pm? or what? There is a temptation to hang on for the price to improve. And I seem to have a strong self-destructive tendency, which I need to control with rules based trading.