There were some excellent posts by Comanchie in this psychology thread.

The summary of his ideas is that the brain performs better when it is prepared for various outcomes. Misplacing hands is my biggest source of tilt. I want to play every hand perfectly, and this leads me to losing focus when I mess up a hand. Lately I've been taking a few moments before a session to prepare myself to fail. Yes, I tell myself that it I will inevitably make some technical errors, have lapses in concentration, and get outplayed. Each time I make a "mistake", I write down a note for reference for when I review my hands in PT.

The objective is to minimize these mistakes by playing in the best mental state, and studying the technical aspects away from the tables. A fast paced 6-tabling session is not the time to dwell over misplayed hands. Get that stuff out of your mind so you can focus on the next hand. If your play is really weighing on your mind, take a break. This technique has been working well for me recently. I have recovered from 2-5 buyin drops to book huge winning sessions, where as in the past I would tilt off a few more buyins or quit. Try to play each hand to the best of your ability, but prepare your mind to accept the inevitable mistakes.