Do not think that God's grace destroys free will. It is resistible in an immediate sense, but irresistible in an ultimate sense, for God knows precisely the amount of grace to provide, in order to guarantee that you do His will in history, even if mysteriously He also knew you were able to resist the grace. Thus, who resists His will? (Romans 9) Is there boasting? Not of yourselves (Ephesians 2), but there IS boasting in the Lord, who works in you to will and to do of His good pleasure, so long as you present your members to be the instruments of His righteousness (Romans 8). You must present the members, and then He does the work, so that you work out your salvation with fear and trembling, rather than for your salvation. For you present yourselves, and He works in you and through you. Only the elect will receive the graces efficaciously that determine them to the final prize.