Evaluate Facts
We often undervalue what we do. Self criticism becomes a habit expressed in our thoughts and our language patterns. Start to evaluate what you do not by how you feel about a situation but by a true assessment of the facts as they really are.
You may feel that you are not a good teacher and criticise yourself for this but if your courses are over subscribed and people obviously want to come on your courses then you are not evaluating the facts accurately but listening to your fears.
A common experience is for people to feel that they are somehow failures because they feel terrified of flying yet they still manage to go on holidays or work abroad. The fact is that their achievement is greater than those who feel no problem with flying. Despite their fear they still manage to fly yet feel failures because they are so nervous. They are evaluating the situation incorrectly. Despite what they feel they achieve.
Turn all events into achievements by changing the way you look at them. Evaluate the facts not your fears.