It is the divine grace or power that comes in the form of self-effort. The divine grace and self-effort, as well as dualism and monism are nothing but the two sides of the same coin of Reality. The grace of God is always available one has to collect it. To win the grace is not easy. One has to earn it by sincere spiritual discipline and effort.
Grace is the cream of that effort our own good Karma.
According to Shankara, if any object other than the Supreme Being the Cosmic Energy Field appears to exist, it is unreal like a mirage, or the presence of a snake in the rope. This knowledge should never be spoken by you to one who is devoid of austerity, who is without devotion, who does not desire to listen, or who speaks ill of Me. It is not for any soul to believe save by the permission of Allah. The study of Gita is meant only for the sincere persons. According to Ramakrishna, one can understand Him as much as He makes one to understand.