Because so long as you are in a physical body you have the nature inherited from Adam, a nature which is nailed the same cross of Christ. A new nature is what the spark of the Holy Spirit ‘grows’ in you as day by day you faiths in His life in your human spirit. You are a new creation hide with Christ, hidden/sheltered from Satan, sealed unto the day of redemption, which for Church Age Christians is the Day of the Rapture.
That ‘faiths’ should be ‘ faithe’ the verb form of faith/belief from the Greek. Typing on a little screen with big fingers, sorry.
BINGO!!! You win the prize. And, as you have a nature inherited from Adam you do not have "free will". Our will is rebellious towards God's will. So, one can do God's will or they can do their will.
True "free will" would mean that we could choose to obey God 24/7. The fact that we don't illustrates to us our rebellion towards the things of God and our need to depend on His guiding help each and every day. This is God's grace to help us through our weaknesses.