I believe self-efficacy is an important concept that can apply to a lot of things in life. Self-efficacy is the belief that one is capable of performing in a certain manner to attain certain goals. wikipedia

Wonderful quote I heard today:

The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore, all progress depends on the unreasonable man.

George Bernard Shaw
Irish dramatist & socialist (1856 – 1950)