We can ask of ourselves even that which we think we cannot deliver. We are even encouraged to do so ("reach for the stars"; "a man's reach must exceed his grasp"). Why can't we see our own true potential but are so quick to grasp others'? We are each endowed with an ego. Even the humblest manure-shuffler still harbors some grandiose fantasy about himself, does he not? To remove that would be to remove his humanity.
The cosmos. A big place. Our imagination. An even bigger place. Are these two universes meant to coexist? Do we create new elements, galaxies, universes simply by dreaming them?
Who doesn't want to spit in Mitt Romney's left eye?