There is a basic principle found in the writings of the Rambam (Hilchos Daos) and other classic Torah sources: "Act the way you wish to be and you will become that way."
We are influenced by our actions. Take, for example, someone who wants to become a kinder person. By doing many acts of kindness over time, the person actually becomes an authentically kinder person.
Each day write down at least ten positive actions that you did. Write down kind words and acts, blessings that you said mindfully, and positive things that you did even though they were hard to do. Write down when you felt grateful, and when you refrained from saying something that would cause another person distress. Write down an encouraging telephone call that you made.
What will happen when you are resolved to write down ten positive actions each day? You will go out of your way to do them. This will have a cumulative effect on your self-image.
(From Rabbi Zelig Pliskin's book: "Building Your Self- image and the Self-image of Others" (Artscroll) Chapter 11)