Mantras definately help- the key is finding the one that's right for you, and sounds like you may be on the way to that discovery.

One thing that helped not only cycling but also the very mental (in more ways than one) game of golf; a book called Mind Gym (by Gary Mack). There's excerpts from premier athletes of almost every sport. I keep a copy in my car and read a few well worn pages before an event (kind of pre-game mental warm up)..

All else fails--- try to old tried and true I THINK I CAN- I THINK I CAN---