Jesus said that he is the vine and we are only branches, and that the only way we can bear fruit is to remain in him(Jn.15:2-5). Without remaining in him(staying close to him in prayer and by reading and meditating on his word), we can not avoid sin for too long. You see, we have an "old man", which is our sin-nature, that seeks to do evil, even when we don't want to( Paul says he struggled with this nature.Ro.7:18;19). The way to overcome it is to do what Jesus said: "Watch and pray so that you enter not into temptation, for the spirit is willing, but the flesh is weak"(Matt.26:41). We have been born again with a new nature, and we must follow after that nature, which wants to do good and follow the will of God. The only way to be able to follow this nature is just stay close to God.

Also, be sure to spend time with other believers. You must always have others praying for you consistently, lest you slip back into sin. And also, you must be sure to renew your mind in the word of God. That helps us resist temptation. The Bible says we must hide God's word in our heart so that we will not sin against him. We must also renew our minds from the way we use to think. Old thoughts stimulate old behavior. So be sure to help yourself think differently by renewing your mind. And finally, always confess sins. In this way, you get cleansed from them and forgiven of them(1Jn.1:9). Demon lose legal rights to torment you then through your sins. Confess your sins the moment you commit them. And Stay away from condemnation: you have been cleansed by the blood of Jesus. No more guilt for you now.

God bless!