You do mental stops or computer stops. Also, how to do you handle after hours / pre-market with your stops?
Always real stops. I don't believe in mental stops. That's just too much work and too much emotions. I don't care if I get stopped out and then it goes up 1000%, doesn't matter to me, there's always a next trade.
For anything after hours or pre market, it all depends on your time frame. If you're a short term trader doing day trading, then depending on your risk level, you may decide to sell or buy during market hours. But again, it all ties to your stops and levels. If it is at a specific level, then you should execute your plan to sell or buy so that you're not in some kind of mental olympics. The price is the most important indicator of performance, so block out all the external noise in terms of twitter, news, etc. What I do pay attention to are macro economics like fed rates, CPI, shyt that matters.
Trading is probably like 80% mental discipline and executing a plan.