A Course in Miracles says, “Sin is not error, for it goes beyond correction to impossibility. Yet the belief that it is real has made some errors seem forever past the hope of healing, and the lasting grounds for hell.” (T-26.VII.7:1-2) This passage points to the old idea of a duel between God and the fallen angel Lucifer (Satan), in which the two battle it out for control of men’s and women’s minds.
We must realize that this myth is a projection of the ego, which is the “Satan” in all of us. But as part of God, as an extension of God, our Will and His have not truly been out of sync. It is only in our mad and unnatural way to operate independently of God that the trouble began–the trouble that is an illusion of reality, but an illusion in which, nevertheless, we still believe.
God does not attack our ego (our “Satan”), knowing that it is only a dream and without substance at all. He waits for us to understand that the way of the ego does not work; He waits for our reestablishment of communing with the Holy Spirit, the only natural way to live. As finite minds, we cannot succeed if we try to live separately from our Source.
So we must give up our inferior judgments to the Holy Spirit, who sees the whole picture. This is natural; this is the way life should be experienced, and we learn this as our bad dreams turn to happy ones under the tutelage of the Holy Spirit.
MIRACLES EACH DAY 
Yes!! You have a very clear understanding of what Satan is . Diverging form Divine Will is indeed among the choices one can make-and it is invariably a bad choice.
abide in him/love and witness reshaping of the ego constantly toward being until the buddha steps forward