Confidence is not some nonphysical quality snatched from the spiritual dimension and installed in the mind. It is the feeling that arises when the body's knowledge of itself is in harmony with a person's dreams.
You don't become a runner by winning a morning workout. The only true way is to marshal the ferocity of your ambition over the course of many day, weeks, months, and (if you could finally come to accept it) years. The Trial of Miles; Miles of Trials.