I've been trading for years and still have this burning question in the back of my head. In general, is it better to trade all day long until the closing bell or is it better to stop once your P&L hits a certain gain or loss for the day? To put some numbers to the question, suppose your goal is $500 a day. All systems you may trade will have outlier days with perhaps a few $2000 days (some on win side, some on lose side). We've all had days with great mornings only to give it all back and then some in the afternoon. And it seems these days always outnumber the days that are vice versa. Now a few assumptions need to be made. 1) You do not "overtrade" - so you have the ability to sit on your hands. 2) You are not worried about the cost of your time - so there's no "time" benefit to leaving your computer before the closing bell. Pure number crunching says if, for example, the systems you trade generate winning trades more than 50% of time, then you should take all signals no matter what time of day or what your P&L looks like. But then again, it may be better (and an easy way to smooth out your equity curve) to stop trading for the day at +$500 or -$500 (whichever you hit first). Those with automated systems, have you backtested anything like this? Thoughts?