Remember that your enemy the devil has the ability to project an image on the screen of your mind. He can amplify his voice into the Theatre of your thinking disguising it as your own thought, with uncanny timing in the moment of your greatest weakness, when the Temptation is greatest to succumb that thought.
A new believer will fall prey to this strategy. Then, the enemy will pounce on him with a barrage of condemning thoughts. "How could you think such things? Now you are a Christian and you should be above that!"
Believers, as someone who has been a Christian for many years I can tell you that you will never be exempt from those kind of thoughts as long as there is a devil on the loose. The great news is that you can become an expert at identifying his voice.
My response to these kinds of thoughts for a long time has been to tell him to shut his mouth. Also, students of God's word can use it as a sword to deflect Satan's attacks.
Not too long ago he was assailing me with physical infirmity. In a dream I saw and felt the demons entering my body and my initial reaction, as I was waking up was to chuckle, "Oh it's just you!"
A physical infirmity is often an attack of Satan. When beset with any manner of sickness your first response should be to ask the Holy Spirit what is His path to healing for you. In this present case, I have his permission to seek the best medical and holistic answers while still getting prayer and continually meditating the word of God concerning healing.
In recent years my response to many of his attacks is to laugh out loud. It is humorous to me that he would come against me with the same tactics that were successful 30 years ago because it shows that he has a very limited arsenal. Now that I have learned who I am in Christ and what are my spiritual weapons, including the ability to command the host of Heaven (Hebrews 1:14), I will tell you that the devil is way more scared of me then I ever was of him.
If that sounds prideful to you then I will tell you the enemy is scared of you too. If you are scared of him it's because you haven't yet learned about the new creature that you have become, who you are in Christ. "Be diligent to present yourself approved to God, a worker who does not need to be ashamed, rightly dividing the word of truth." 2Timothy 2:15 NKJV