Knowledge structures. The more knowledge you learn, the more subtle patterns appear. Consider learning English. The word "good" may be sufficient until you know words like "fine", "excellent", "stupendous", sublime."

Social comparisons. When you start, you may compare yourself to your peers. But the more you learn, the more you compare your quality to experts. Unfortunately, this is not always helpful.

We may feel that we are not smart enough to do what we do. One explanation for this is the Dunning-Kruger effect: when you are incompetent, you can't know you're incompetent and can't properly assess your own competence.

Research shows that incompetent students think they ...