I have only multi tabled a few times and its usually a MTT and a SnG and not more than 2 at a time. For me I do better when all of my concentration is focused on just 1 table. Paying attention to everything thats going on at the table. When I multi table that doesnt happen and I end up only playing the cards, and poker is not just about what cards you hold in your hand.
But, I have to agree with jordan, when multi tabling going on tilt shouldn't happen as much cause you get 1 bad beat you still have the other tables to go to.
For me though, I don't go on tilt often, Ive always been a relaxed person who takes the good and the bad all the same, its life shits gonna happen, same as in poker. If I do go on tilt, I get away from the table. I go do some physical activity. Take a hike, do some yard work, workout, whatever, but get off the computer and away from poker if your on tilt. I know its not easy to see when you yourself are on tilt, but if you can it will probably save you a lot of money at the tables.