When I'm not feeling that extreme confidence I felt, and it is natural, humans tend to lose some of the touch in the virtues they learned if they aren't in constant exercise with it. What I do is, I get away from everything, family, friends, car, etc. w/e get away so you're alone, now have some nice quiet music in the back ground, very lightly playing please because the lyrics might deter your mind, and finally what I do is I read some tips that helped me build up my confidence and asking a question at Sosuave forums with reply's from other Donjuans... sometimes even a small comment from them boosts back that confidence.
You just have to keep putting yourself into situations where you're constantly using confidence to get something handled to keep it up, and eventually you'll go longer periods of time without having to lose "touch" of that confidence.
