With this quote from John Newton the writer of "Amazing Grace", one can really rest upon the sovereignty of God for one's peace of mind. When he wrote this quote, he must have had Job 13:15 which says, "Though He slay me, yet will I trust in Him: but I will maintain mine own ways before Him." Job knew that God was in charge of why he was suffering all those stuff and that is the only way to win against one's own carnal mind. I dare not trust my mind or heart that I was born with because the only power I have against sin is in the Lord Jesus Christ. I did not get saved and left alone but instead, I got saved to have daily fellowship with my Lord and Savior, Jesus Christ. Nobody gets saved and God leaves them alone. Instead, when God saves the person He also goes on to work in them (Philippians 1:6, Philippians 2:13).
2 Corinthians 10:3-5 says, "For though we walk in the flesh, we do not war after the flesh: (for the weapons of our warfare are not carnal, but mighty through God to the pulling down of strong holds;), casting down imaginations, and every high thing that exalteth itself against the knowledge of God, and bringing into captivity every thought to the obedience of Christ; and having in a readiness to revenge all disobedience, when your obedience is fulfilled." That is really the best advice that any Christian can take so they can win more in their daily battles because the carnal mind is definitely destined to lose against one's sinfulness. Only God's grace has true power against sin (Titus 2:11-14).