Learn to separate what happened to you from what you decided it means about you.

Events arrive without commentary. What you carry afterwards is not the event itself but the conclusion you drew about yourself in the middle of it, often at an age or in a state where fair conclusions were not really available. The rejection happened. That it meant you are unwanted was added later, by you, under pressure.

Take something painful from your history and separate the facts from the verdict, literally on paper if it helps. Facts on one side, meaning on the other. You cannot change the first column, and the second is more open to revision than it has ever felt.