Hebrews 2:8

Thou didst put all things in subjection under his feet. For in that he subjected all things unto him, he left nothing that is not subject to him. But now we see not yet all things subjected to him.

This verse emphasizes the differences between man's potential and what he has actually become. The grave consequences of the fall of Adam, the expulsion from Eden, the cursing of the ground, and the imposition of the penalty of death - all these things have for long ages frustrated the human attainment of the purpose of God in man. Instead of all things being in subjection to him, man finds that he cannot even control himself; and beyond that there are countless things that he cannot subdue or subject to himself, so much so that unaided humanity must ever despair of any true realization of the royal dominion assigned in Genesis 1. But Jesus Christ came, taking upon him the form of a servant, providing for the plenary discharge of man's sins, tasting of death for every man, and rising to heaven with man's glorified nature upon him, and thus on man's behalf achieving that dominion of man intended from the beginning. Although prior to this writing of Hebrews, Psalms 8 was never understood as Messianic, yet it is only in the Messiah that it could ever be true.