I can make a real difference

The difficulty is that you almost never get told. A teacher doesn't hear which sentence stuck. Whoever talked someone out of a bad decision at a kitchen table gets no confirmation, ever.

Which means the evidence arrives in the wrong direction. You know exactly who made a difference to you, and most of them have no idea that they did.

Assume the same is true of you. Somebody is carrying a line you said once and cannot remember saying. Real difference is largely invisible to the person making it, which is a poor incentive system and a fairly accurate description of how the world holds together.