Your confidence must rest on this fact: Unclean thoughts will not stay where the love of Christ reigns supreme. They are as panicked by overhearing your conversations with Christ as an escaped murderer would be upon realizing he has been spotted in town. And well they should be--for your holy thoughts will track down these evil thoughts and kill them on the spot. Both the trial and the sentence will be speedy.
Secondly, steadfastly resist sins of the heart, thereby showing where your loyalties lie. We need to be constantly reminded that heart sins are sins as much as any: "The thought of foolishness is sin" (proverbs 24:9. Every point of hell is hell!
Lust, envy, and murder are sins when committed in the heart, the same as in the outward act. Such thoughts cannot run rampant in a Christian without serious consequences. Your spirit is the dwelling place of the Holy Spirit; He takes up the whole heart for His lodging. When He sees you have leased out rooms to the lusts of the devil, it is time for him to be gone. If you cherish His Presences, declare you loyalty to Christ at Satan's first knock by renouncing every thought that is not a willing captive of God. William Gurnall