One teacher believing in you can rewrite a story. Be that for someone younger.

Belief from an adult works because it arrives from outside your own head, where it cannot be dismissed as wishful thinking. A single person treating you as capable gives you something to test, and the testing often produces the capability. It does not take much: a sentence, or being asked to do something slightly above your level.

You are already older than somebody. A younger sibling, a kid on a team you help with, a freshman at your school. Say the specific thing you have noticed they are good at.