Please understand that "of his own will" doesn't mean a will entirely cut off from God -- which is a dreadful, horrible thing to even think of --- but a will which is in itself a gift of God, yet truly his own.
God does not have the only Will in the universe. That would be the claim made by Islamic theologians, of Allah.
And here's another one:
Council of Trent, session 6, Canon 21: “If anyone says that Jesus Christ was given by God to men as a redeemer in whom they are to trust but not also as a lawgiver whom they are bound to obey, let him be anathema.”
If you agree with that statement from Trent you aren’t trusting Christ alone. Salvation conditioned on Christ’s work plus any necessary condition of performance (Rome’s sacraments for instance) stands in stark contrast to the biblical way of salvation. Works and grace absolutely cannot mix. If salvation comes by grace, then it’s not by works. And if it’s by works, then it’s not of grace (see Romans 11). We are saved by grace through the means of faith unto good works (see Ephesians 2:8-10). But it’s never faith that saves, it’s the object of faith—Christ—who saves.
As for the will, God has the only libertarian free will. Man’s will is in bondage to sin due to the Fall. No man will ever willingly choose Christ. No man in his natural state seeks after God. God has to make the man willing first. A man who is truly willing has been regenerated or born again. The New Birth is a miracle, an act of utter grace, performed in the heart by the Holy Spirit.