Positive self-esteem operates as, in effect, the immune system of the consciousness, providing resistance, strength, and a capacity for regeneration. When self-esteem is low, our resilience in the face of life's adversities is diminished. We crumble before vicissitudes that a healthier sense of self could vanquish. We tend to be more influenced by the desire to avoid pain than to experience joy. Negatives have more power over us than positives.
If you face life without confidence in your own powers, you succumb too easily to setbacks and adversity; you lack the will to persevere.
It is true that people are sometimes hit by adversities beyond their control. But those so affected are better helped when they are awakened to the resources they do possess than when they are told they don't have any.