This depends so much on the current situation right in front of me. Is the day just starting, or am I about to finish it for today ? Is it a very fast volatile market, or is it more of a slow day ? Am I ahead already, or do I already have an ugly loss in the book ?
Depending on these and other factors, I might usually want to get out of a trade once I see that the market is not really moving the way I want. Many times this will be already at -1 tick, or -2 or -3 ticks. Sometimes I might be expecting a breakout or snapback, but it does not come, so I scratch the trade or get out with 1 tick profit if possible.
Other times the market has maybe already fooled me multiple times, and I get pissed and stubborn. Then it can happen that I let it run much more against me, maybe 10 ticks, maybe even 20.
Or on days when I am very nicely ahead, for example I made already 30 ticks profit. And the past few days have all been good. Then I might want to take some more risk, like playing with the banks money. I might accept to sacrifice the 30 ticks that I already made for trying to catch a bigger move, from a breakout for example.
Sometimes it works NOT, and you go home with zero for that day. Sometimes it works, and you go home with your biggest day for the month.
What I try to do is to finish every day positive, which of course is not possible. So what I really try to achieve is to finish every week positive, which works most of the time. No perfection needed. It is ok to have a -2000 day if the rest of your week is +500, +3000, +800, +4000.
I liked lescor's thread very much, he was a great example that you dont have to and should not strive for perfection in trading. Many good things to learn in his thread:
https://www.elitetrader.com/et/threads/grinding-it-out-day-after-day.187730/
So like I said, I would not overanalyze this stuff. I like math and numbers, but some things are very hard to quantify. The market is all about psychology and your experience, your psychology interacting with the mass psychology of the market. There is no computer yet that can grasp all these thousands of fine nuances. Just like there is no computer yet that can form and bake the perfect cake. With some things, human brain and hands are still ahead of the machines.