We learn that the Creator created a Kli (vessel) called the soul of Adam ha Rishon (the First Man). That Kli was in D vekut
(adhesion), in equivalence of form with Him, meaning in complete bestowal, but without differentiation from Him, without its own desire. When its own desire was added to the Kli, then according to its independent desire it wanted to draw much greater Light than filled it at first...