What is the difference between confidence and overconfidence?
 

Confidence based on facts and knowledge and overconfidence based on speculation. There is a small difference between confidence and overconfidence. Yes, I can do this work is self confidence. But only I can do this work is over confidence.

Or you can say that- confidence is an internal believe that I am a right person for this job and overconfidence is thought that I am only the right person for this job.