If man chooses the path of the Torah, he can neutralize his selfish body and desires in such a way that they will no longer act as an obstacle between him and the Creator. Man and the Creator unite. This union is a throwback to the Procreation State, before the descent of the soul into this world, before the soul is “handicapped” by selfishness. Moreover, by correcting his selfishness man can climb the rungs of the spiritual ladder and reach the level of the Creator. Some creatures are devoid of selfishness and therefore have no tool to progress and remain at their initial level.
Courtesy of http://www.youtube.com/watch?v=VXoIG8YYKqs