Key of self confidence.............

yes, its true ....the more you practice, the more u'll be confident.....

but believing in all those skils is also essential ......

example .....suppose a person who is working day and night and forget every thing else ... some  people also used to sleep 4 hours a day ... and such many things ...

But on D-day , they can't give their best shot ..not because they haven't practiced ....But because they have strained themselves so much ...that making good performance is a pressure in itself.

Exactly

PREPRATION is the key of confidence......