“I hate vain thoughts: but thy law do I love” (Psalm 119:113)
The mind is the battlefield between the light and darkness. It is up to us to decide with which substance to fill it in. Are we entertaining vain (Useless/evil) thoughts in our minds or are we saturating it with God’s Word? This would be your answer if you feel powerless to sin.
I encourage you to start saturating your mind with what is holy and meditate on the Word day and night and do not let cracks in your fortified walls for the enemy to infiltrate. Remember, the battle is already won in Christ Jesus.