A person creates a low self-image with his thoughts. Someone who constantly repeats demeaning self-talk will build a low self-image. The more he continues thinking and focusing on negative thoughts that lower his self-image, the worse he will feel about himself.
Being around an extremely critical person can be very distressful. But having a very active inner critic frequently criticize what you say and do without letup creates even more distress.
When you consistently think thoughts to build your self- image, these positive statements become stronger and stronger and the old negative ones get weaker and weaker. The neural pathways to the recent life-enhancing thoughts are enlarged and your mind will find it easier to travel this more beneficial path.
Keep in mind that every young child has immature ways of thinking, speaking, and acting. As people grow up the vast majority think, speak and act in more adult ways. Even though the childish ways of thinking, speaking, and acting are stored in the brains of adults, the more mature behaviors become automatic and spontaneous.
(From Rabbi Zelig Pliskin's book: "Building Your Self- image and the Self-image of Others" (Artscroll) Chapter 32)