I could speak for hours on this topic (and maybe I will in the future) but for now here are some random thoughts...
- in Barry Greenstein's book Ace on the River he discusses that pros nearly always quit a game at less than their peak stack, and this is a good thing. If you often quit at your peak you are probably quitting at the precise time when your edge is largest. Also, by losing a little back and then quitting fish will enjoy playing with you more (this is more relevant when you often play with the same people).
- I have played many long sessions in my life, and often in them I was winning a lot, then winning small or even losing, and then winning a lot again - if you play a really long session chances are better that you will have results that sort of mimic our mental idea of "the long run", ups and downs, swingy, etc. If you play shorter sessions you will only have usually one iteration of this (maybe you get up a lot and then back near even, or you lose a bunch and then win most of it back) and you might ascribe too much meaning to what happened. Also realize that the mid-session swings you are experiencing are all relative, to someone that routinely plays 20 hour sessions a 50 bet swing in any direction would most likely not be very noteworthy. To someone who plays 2 hour sessions, that would be a large swing.
- Like in competitive sports, the best poker pros I have observed seem to have a "step on their throat" attitude. When they are winning a little bit their primary thought is "I can win a lot today", when they are winning a lot they think "I will bust them all". In my experience I have found my personal happiness with results is best achieved when I take this attitude BUT I also allow myself to quit and 'lock up a win' if I lose some back and start to think about my current session results in any way. Sometimes the game is very good and I am focused and I can continue playing because I never really even think about the fact that I was winning X and now I'm only winning X-Y.
- An excellent time to ask yourself "should I quit this game" is when a noteworthy player (good player or bad) enters or leaves the game, OR when a noteworthy player changes seats and it has some effect on you. There might be small reasons you are doing well that you don't realize and then they go away when somebody moves seats, it might subconsciously affect your level of play as well.
- When I am winning and don't have somewhere else to be, the reasons I will quit a game are as follows, and they are in descending order of importance:
- if I ever have a thought similar to "hmm I could quit right now", I force myself to quit immediately, this is so important I can't even tell you how much happiness this has generated for me.
- if I start losing some back and become consciously aware of it, this usually directly leads to the previous point anyway.
- if game conditions change adversely, note that this is the third most important to me, not the first (as I bet some would think), when you are winning these things don't hurt you as bad as when you are losing, you are playing your best, people are playing worse against you, etc. You can often play in crappier lineups, less comfortable situations, etc. when you are winning and play them well.