With technology, that role has not only changed, but it has definitely diminished. Children now live in an ecology of technology. The gradual transition described by Erickson from the child's autosphere to the social macrosphere no longer exists. The brain of the young child is overstimulated by the new multimedia environment with its sound effects, and rapidly changing, attention grabbing images. I do wonder about the effect on the attention span of the developing brain.
Frustration is a feeling state that emanates from our innate aggression.
If it cannot be tolerated, aggression in words or in deeds is the result. The child learns to do without some things, and to be patient and wait for others. Primary narcissism is tamed. Tolerance requires the development of empathy. And empathy requires time to think about another person while putting aside one's own needs or wishes.