kill it by lunch and enjoy the afternoon if you're up enough/in profit. OR go early afternoon to see if there's anything. OR if in lik futures and you take a couple of rough hits, just call it a day. OR if you're one of those special ones, you get to go the whole day!!
You should only stop trading for the day when you have a statistical reason for such. For a simple example, lets say statisticallly most of your profits occurs before 11am est and after that you have a high probability to lose money. Statistically you should stop trading by 11am est until you can figure out (resolve) what the problem is with your methodolgy for trading after 11am est. This reason alone is why some trader's say knowing when not to trade (statistical proof) is an edge and improves your profit curve. Mark
If your setups are there you trade. If they are not you don't. To me, it's that simple. Some days you win and some days you lose but if your setups have a reasonable probability of success you need to take each one as they come.
Yes, I think it is totally personal when someone choses to stop trading for the day. People can stop whenever they want.
When I have my favorite dish for supper, I could go for 2 helpings or more. When it's leftovers, one is enough. Same with trading. Define YOUR level of COMFORT and GREED and STICK TO IT!