When i use to play poker i would always try to leave when ahead. It would make me feel better about my decisions. As you get tired and get bad beats you tend to steam. Although you are not supposed to and your wins are in term of BB per hour. I do the same with BJ. Play short sessions and leave when im up. Its better for my mental state. If i play for a long time a lose track of count more often and make errors. So in that sense its +EV. But i do understand that im just a beginner and most of you dont have that problem.