The key to defeating sin, the key to mutilating the flesh is in your mind. So many Christians run away from God because they feel that they just can't stop sinning. They give up and don't take their opportunity to make a difference in the world. They allow their flesh to win.
" For those who are according to the flesh set their minds on the things of the flesh, but those who are according to the Spirit, the things of the Spirit.
For the mind set on the flesh is death, but the mind set on the Spirit is life and peace,
because the mind set on the flesh is hostile toward God; for it does not subject itself to the law of God, for it is not even able to do so." Romans 8:4-7
I believe the first thing to do when struggling with sin is to change your thoughts. Stop saying with your mouth, God will give me strength while thinking how can I make it today? The more your mind thinks the opposite the more your flesh will gain control. For an example, a wife who loves her husband and respects her husband outwardly but fantasize about sneaking away with the guy next door. How long do you think it will take before she allows her thoughts to take over?
When experiencing a thought in direct conflict with God's word; a thought that is not of the fruit of the spirit (Galatians 5:22-23) stop it! Ask all your thoughts to check in at your spiritual hotel (your mind) and if it is not a thought of the spirit kick it out. Stop it, before it can grow. Don't reason with it, or challenge it, or ask about it, just kick it! Kick it out of your mind and away from you before it can grow and get out of hand.
"Finally, brothers, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirableÂif anything is excellent or praiseworthyÂthink about such things.Philippiansns 4:8