At some point you have to believe it before there’s proof. Otherwise the proof never shows up.

Evidence comes from work, and the work usually requires believing up front that it is worth doing. Waiting for certainty before you start guarantees you stay uncertain. That is not positive thinking. It is just the order these things happen in.

You do not have to believe in the whole outcome to begin. Believe that the next month of effort is worth spending, then check what came of it. Small confirmations are how a bigger belief eventually gets built.