When you feel inadequate, there is usually someone you are comparing yourself with.
In reality of course, you’re making yourself feel like this. But humans being humans, we’re always thinking about what others might be thinking.
By comparing yourself to another person, you have put that person on a pedestal. You have assumed the person is smart and clever. However, you don’t really know what is going in that person’s life. We all suffer. That person you’re comparing yourself to does as well.