In his old age, when he could no longer see to read, John Newton heard someone recite this text, ‘By the grace of God—I am what I am.’ (1 Corinthians 15:10)._He remained silent a short time and then, as if speaking to himself, he said: “I am not what I ought to be—ah, how imperfect and deficient! I am not what I wish to be—I abhor that which is evil, and I would cleave to that which is good. I am not what I hope to be—soon, soon I shall put off mortality, and with mortality all sin and imperfection! Though I am not what I ought to be, what I wish to be, and what I hope to be—yet I can truly say, I am not what I once was—a slave to sin and Satan! I can heartily join with the apostle and acknowledge, ’By the grace of God—I am what I am!’ “_
The quote above is taken from the Grace Gems website.
See also Romans 7:15-25