I say “you gotta believe” a lot, because… well, I believe it, philosophically and biologically. It’s a motto and a mantra. I don’t think I’ll ever know if I picked it up subconsciously somewhere, or whether it’s just one of those examples of convergent phrase evolution.
Turns out there is a specific person to whom it’s ascribed, though, and his name was Tug McGraw, and he died yesterday. His obituary is sad, but it’s also good reading. He lived what he said.