Whether we realize it or not, each of us carries about with us a mental blueprint or picture of ourselves.
It may be vague and ill-defined to our conscious gaze. In fact, it may not be consciously recognizable at all.
But it is there, complete down to the last detail.
This self-image is our own conception of the "sort of person I am".
It has been built up from our own beliefs about ourselves.
But most of these beliefs about ourselves have unconsciously been formed from our past experiences, our success and failures, our humiliations, our triumphs, and the way other people have reacted to us, especially in early childhood.
From all these we mentally construct a "self" (or a picture of a self).
Once an idea or belief about ourselves goes into this picture, it becomes "true", as far as we personally are concerned.
We do not question its "validity", but proceed to act upon it just as if it were true.