Are you currently being overcome by a besetting sin? After you confessed and asked God to forgive your wrongdoing, you promised never to go back to that same thing again, and you sincerely meant it, only to find yourself doing the same thing again. If this experience happens often, you might start to think it is pointless trying to serve God. Are you giving up on serving God? Don’t! Such a circumstance isn't new to believers. A lot of true believers have gone through that phase.
To defeat this phase, which is temporary, perverse. If you fall into the wrongdoing, do not stay there. Ask God for mercy and get back on your feet. Never stay down; continually find your way back to Jesus, receive cleansing, and continue with the Lord Jesus.
Also, identify that specific area of weakness and start to pray on it using Romans 6:5-18, personalizing the scriptures. Avoid anyone that will easily take you back to that sin you don't want to go back to and sever such a relationship. Pray always in the Spirit asking for God’s help. Have no idle period, ensure you engage yourself in what glorifies God.
If the Lord Jesus could still commission Peter to proceed from where He stopped after three terrible denials, it doesn't matter how low you have fallen, God can return you to His original plan for your life.