IMO

Play one less table than you are confortable playing.

Boredome is your enemy. Before you add another tables, have notes on at least half of the table you're currently playing, even when using a HUD.

If you quit ahead and before you get tired then you won't be forced to quit behind and tilted.

Leave a table when you lose 3 big pots. Make it two if it's the same villian. When you lose 3 pots or 2 to the same villian you may have tendancy to "get my money back from that donk"

Again, IMO