I matter and what I have to offer this world also matters.

Mattering is hard to feel from the inside. It's nearly always visible to other people before it's visible to you.

Somewhere there's a former student still using a phrase their teacher said once, offhand, on a wet Thursday, and they've never mentioned it. That teacher went home that day certain nothing much had happened.

Most of what you contribute lands out of sight. The effect isn't diminished by your not seeing it. If you're waiting on evidence before you'll accept that you count, the evidence exists — it's simply held by people who assume you already know.