If you really want to eat glass, then you will do it.  You and I generally do what we want, even if what we want to do is harmful to us or to others.  But what if God’s Spirit changed you so that you no longer liked to eat glass?  Would you complain that He has taken away your free will?  Or would you give thanks to Him that he gave you a new desire that saved your life?  Left to ourselves, we choose what is harmful to our souls.  Thanks be to God that He changes our hearts so that we choose Jesus!