Man is choosing whether to do his own will or to do God's will as known through the Commandments, the Scriptures, or the precepts of the Church. The choice lays open to us. Now certainly, you would agree that our will and God's will can coincide, even those who are unregenerate. But in those cases where they differ (should I steal or not?), I contend that the choice exists between satisfying our own materials needs and purposes, or satisfying God's Will as it is made known to us.
Regards
If that is the case, isn't it God who gives us our understanding and our desire to do His will?