How do demons know exactly what tempts me?

The demons have been studying mankind since the beginning, preying on the weaknesses of each personality. You could say the demons build a psychological profile for each person, and depending on how that person is built, their inclinations, what tempts them, all of the devil's attack goes to that. Take somebody who is intelligent. From a young age the demons tell them, you're smarter than other people, you're better than other people.

They stop glorifying God for the mind God gave them and start using a God-given gift to build their own ego, with the demons cheering them on. By high school they're looking down on people, then speaking down to them. Their personality becomes warped by these demonic thoughts, which they can't get rid of because they don't even realize they're from the devil.

In adulthood they think whatever they think should happen, so they try to control life and the people around them, and they become insufferable. When things don't go their way, they're thrown into despondency and anxiety. Or take somebody prone to perfectionism. The devil says, God is perfect, you should be perfect, and if you're not, you're not worthy. This happens to a lot of Christian women.

They begin to see themselves as a failure before God, and then project onto God that he is upset and disappointed with them. But it's all within their own head, the byproduct of destabilized thinking. As a priest hearing confessions over the years, you realize people have been thinking some thoughts since childhood, and the fear, anxiety, and depression are the byproduct.