When a person has been mistreated, the person can learn I am not important. Someone else is important. That thought (conscious or unconscious) can influence every decision in life.

As a therapist, one can readily and professionally say I am not important. Someone else is important. Thus the job of therapist, or of helping person generally, can fit very well with the underlying thought created by the mistreatment.

The person who becomes a therapist may not be able to escape the belief in their unimportance, but they transcend it. The person finds a way to become and feel important--by learning how best to make others important. The person becomes important and unimportant at the same time. And heals.