then it leads to the conclusion that we are not responsible for our moral actions and choices. Then it means all our moral actions and choices are the results of God's will. This would lead to dangerous and unbiblical conclusions.
Free will has to be possible. If not, then there would have been no rebellion, no pride, no sin, and no fall.
Starting from Adam and Eve, they were given a choice. The manifestation of that choice was the tree of life and the tree of the knowledge of good and evil. So does everyone of us have that choice.
I think the mystery is that God is able to work in our hearts that there are people who willing surrendered their wills to His, and they became one with Him. That's what Christianity is about, to become one with Christ. It is a mystery indeed. To be in Christ, be part of Christ, yet still retain our individuality.
And Jesus was eventually born, all the prophesies fulfilled because many people were like Mary, who said, according to Your will, Lord!