Professional trader know the methodology of trading. Most skillful trader didn't trade with emotion they have their predetermined exist plan and have good trading plans.
but for me, i think not all skillful trader didn't trade with emotion, i think its because the trader itself should have many experience when they do trading and this will give impact for them. the more experience they have, they can control their self when they do trading and its really important for us especially for me, to control myself to avoid the greediness.
Emotions is really a big problem with doing trades because it will affect you psychologically and if this will happen to you, you could not able to decide properly and might be derailed on your listed plans or methods that you should do thats why its really hard when you let your emotions overcome you when you are in the middle of a trade.