This is a question about the difficulty of dealing with the constant failure of attempted self-improvement despite the best of intentions. It's one we all must have asked ourselves from time to time.
Q. I have a favourite sin that I cannot seem to overcome. Each time I commit it I resolve to never do it again. I lament to God and myself. I feel ashamed, I chastise myself, I plead for divine support and guidance. Sometimes I even make it through a few weeks without repeating it and feel pleased with my progress, perhaps even imagine that I am finally free of it and then...with sickening monotonous regularity my weakness reappears and my resolve crumbles...and I break my promise to myself and to God again. One tries to just dust oneself off and repent and carry on but after a life time of being unable to overcome the sin (worse still I find myself eventually dismissing my actions as harmless and not a big deal and deciding to 'cut myself some slack' or convince myself 'everyone else is doing it anyway') eventually I am starting to feel very worn down and like I must surely be exhausted God's tender patience...I pray I am not yet a lost cause!
A. None of us is perfect or we wouldn't be here. We are all sinners or imperfect or however you want to look at it, and we all fail in our attempts to get better and to overcome sinful ways. But, and this is the point, to be aware of sin in ourselves as sin is a huge step forwards. Many, I would say most, people aren't aware of this or, if they are, they justify it or cover it up. You may make the same mistakes over and over again but each time you repent and feel you've let God down you are making an advance. I can tell you at 60 I still find myself doing things that the Masters chastised me for nearly 40 years ago (mostly to do with irritability, bad temper and pride). Pathetic, isn't it?
But there we are. It takes a long time to overcome bad habits and weakness. The fact that you lament, the fact you chastise yourself means that you are overcoming it. Overcoming sin is swimming against the tide of your nature. It requires constant self-observation and means that many battles will be lost. But God has seen it all many times and his capacity to forgive is endless. You won't exhaust his patience! As long as we truly repent and keep trying that's all he wants. But we must keep at it and not get discouraged by failure. That's just the voice of the devil saying "Why bother? You're never going to get over this. You may as well not try". Or else he says "You're hopeless. You keep letting yourself and God down. You're a disgrace. You're so disgusting that you should be ashamed of going before God yet again with this sin on your conscience." All that is a big fat lie. God loves you. He knows you better than you know yourself. He understands all your struggles and he will support you all the way. There is nothing you can do that will turn him against you just so long as you keep turning to him and acknowledge your shortcomings. Never give way to despair. That is the temptation to discourage you from further striving.
There's no magic formula but there is prayer and remembrance of God. Never be ashamed of going to him and confessing your failures, even multiple times. All he wants is that you keep on keeping on and don't lose faith. There will be many opportunities to do so but these are just tests. We have to be tested to prove our mettle and make us stronger so don't be deterred by these. You will probably be assailed by the forces of darkness since these attack anyone who sincerely puts his foot on the spiritual path. They will attack through your own feelings and thoughts so be on the alert for anything that might put thoughts of darkness or despair in your mind. Bring the light of God to bear on these to flush them out. Raise your mind up to a higher level of purity and goodness, maybe even envisioning a pure white light surrounding and protecting you. I think it's better to do that than to confront them directly through resisting them. Just ignore them and replace darkness with light.
And never give up. It's a long road but the prize is great. We are supported all the way but it's not easy to feel that. So pray and keep praying even if you seem to have no response. The greatest saints went through what you are going through. They had temptations. They failed but they kept going, their eyes firmly fixed on the reality of an always loving God.
The attempt to turn oneself around is the most important thing anyone can ever do. Next to this the achievements of the greatest artists are negligible. Never mind the whole host of pointless pursuits most people seem to regard as achievements these days. You are privileged that you have been given the chance to do this so bear that in mind and make sure you don't ever get discouraged.