Of course, self-belief is more than just common advice. It's at the heart of selling, of creating, of shipping, of leadership…
Telling someone, "believe in yourself," is often worthless, though, because it's easier said than done.
Perhaps the alternative is: "Do work you can believe in."
Not trust, verification. Not believing that one day you'll do worthwhile work. Instead, do worthwhile work, look at it, then believe that you can do it again.
Step by step, small to large, easy to difficult.
Do work you can believe in.