It's a good question, for sure, and one that crosses every poker player's thoughts from time to time.
I think that if you can look to your Real Life, you'll find cues as to what sets you off on the poker table. Just as traffic or bad drivers upset some motorists, so do the bad calls of others often affect us.
I just do the best to remind myself that I cannot control the traffic (nor the plays by others nor the cards that are dealt), and to just surrender to the process and focus on the things that I do have control over (my plays and my reactions to others' plays).
Off the tables, I participate in a lot of meditation, visualization, positive self-talk, Tai Chi, anything that resolves the wholeness of my being... as a result, I am usually quite balanced on the tables as well and don't really get affected by too much.
I did find an article which might assist you: http://www.bluff.com/magazine/make-a...-positive-293/
Wish you the best.