I want to do what is right, yet I fall again and again. I repent, get up again, and attempt to change; however I get depressed when I seemingly fall again and again. How can I break the cycle of sin? How can I grow in the ability to fight sin via Christ and his transformative grace rather than by my own devices?
First, you are not alone in your struggle. Even the Apostle Paul battled with indwelling sin as a believer. Just read Romans Rom 7:19 “For the good that I would I do not: but the evil which I would not, that I do.” His cry is a common one for believers, “O wretched man that I am! who shall deliver me from the body of this death?.” The beautiful answer is, “I thank God through Jesus Christ our Lord” (v.25).
Second, we should remember that the Lord leaves sin in his people to foster humility. Knowledge of sin has an emptying influence, especially besetting sins. They bring us low, tender, and needy. These sins should be an ever-present reminder that we need the grace of God moment by moment. Sadly, the “cycle of sin” will continue until the day of your glorification. New victories will be given, but only to give way to new battles. It is a fight, a warfare, a race that must be run.
Third, battling a besetting sin is only possible when we realize that effort and personal strength alone won’t do it. We need the Spirit’s influence and help to fight daily against it, where our growing desire is for holiness. Prayer becomes key. Taking every thought captive to the Lord (2 Corinthians 10:5), asking for strength in a time of temptation (2 Corinthians 12:8-10), resisting and fleeing from the opportunity (James 4:7) are all vital. These are God’s tools for us, not necessarily to overcome besetting sins, but to wage a valiant war against them. If there is a silver bullet to killing sin, I do not know what it is. The only victory I can find on this side of eternity is “even our faith” (1 John 5:4).
I have been encouraged many times by the words of John Newton in a letter he wrote to someone asking the same question you did:
As to the remedy, neither our state nor His honor are affected by the workings of indwelling sin—in the hearts of those whom He has taught to wrestle, strive, and mourn, on account of what they feel. Though sin wars in us—it shall not reign in us. And though it breaks our peace—it cannot separate from His love. Nor is it inconsistent with His holiness, and perfection, to manifest His favor to such poor defiled creatures, or to admit them to communion with Himself; for they are not considered as in themselves—but as one with Jesus, to whom they have fled for refuge, and by whom they live a life of faith.
Hope this helps!