For a long time, my rules for level 2 consisted of the following two requirements. Number 1: walk when you quit for the night or day or session. Basically, I quit playing on my tables when I was done. Number 2: quit when people leave the table and you suddenly find yourself in a shorthanded game when what you signed up for was a full ring. Basically, I don't want to switch my strategy and considerations for one table when I have 3 or 4 other tables on which I'm playing my normal full ring strategy.
I suspect that many people have the same requirements for quitting level 2. Let's examine what the underlying principles, ideas, and tendencies are for this approach. I'll draw from my own experience. I tend to think that when I sit down at a full 10 player table, I'm better than 9 of the players at the table. This leads me to infer that I'll be getting the best of all of them; hence there is no reason for me to leave the table. You may have the same thought. We may be right; we may in fact be the best player at the table, but this doesn't equate to getting the best of it. Just because you are better doesn't mean you will win. I don't know if you know this, but suck outs happen in this game. The worse the players at the table are, the more likely you will be sucked out on. If this happens repeatedly, you may become upset and angry with tilt not far behind. Even if you don't tilt you will find yourself down after these suck outs, and this is where the problems magnify.
You've been sucked out on repeatedly. You had the best of it, but these idiots keep getting bailed out. You're stuck, but on this table you just need to keep playing to make it back. These guys are donators, obviously, so just let them donate. But alas, you just can't seem to get it back. You win a couple of pots, and then along comes another bad beat and you lose that hand. You keep playing well, but you're still stuck. You play, and play, and play, but still stuck. You pick up A-A and several players call your raise. You bet the flop and get raised; you push and ‘the idiot' calls with Q-3 which equals 2 pair in this hand and suddenly you're stuck worse. You rebuy, because of course these ‘idiots' can't keep a good player down. Now perhaps you win a slight amount, but not enough to cover your losses. Just some bad luck. Your eyes finally get heavy and you play one more orbit, and now you walk. You've quit, but too late.
Why did this happen? Well, it starts from thinking you are better than the other players. This leads one to think that one will win money on this table. Played properly, that is true. Another thought, however, creeps in. One starts to think that one deserves to win. Then another thought worms its way in. One starts to think that one need only continue to play to turn it around. This thought process leads one to overlook the problem involved at this table. You sat down with the aim of playing poker, but this table is not favorable to your normal game. It's favorable to someone who limits play to getting the nuts and playing it hard. Now you have two options. Play differently than your normal game, or walk. If you have several tables up at the same time, then it can be difficult to remember which table is the one where you have to play in a vastly different way from the others. This is a reason to walk. Another reason is that when you are stuck, you tend to want to win that money back, and you play harder than you normally would, getting yourself into marginal situations that you aren't used to. That is a recipe for disaster.
When you find that you aren't getting the best of it, walk. This doesn't just mean, when you find yourself at a table full of sharks, walk. It means when you find yourself at a table with a certain mix of players that is not conducive to your playing style, even if the players are all worse than you, walk. Quitting is not the easy thing to do (contra the common saying), particularly in poker. Folding a big hand is hard. Walking from a table full of bad players is hard. Unless you are willing to adapt (and by this I mean REALLY adapt) to each table, quit. Quit that table, click over on the lobby and find another table with a mix that suits your game. Be aware, however, that the character of a table changes over time as players leave and new players join. What starts as a good table for your game can quickly become a bad one, and when that happens, level 2 quitting is a good option.