Eternal life is free, and once received, it cannot be forfeited or returned. It does not depend in any way on my good works, obedience, or perseverance. While good works are commanded (Gal 6:10) and rewarded (1 Cor 3:10-15), they are not required to validate my salvation. Furthermore, no amount of sin I commit can undo what God has accomplished. My good works did not save me, and my sin cannot unsave me. Salvation is of the Lord, not of me. He alone gets all the credit and glory, for He alone saves.