There is no greater good than knowing your mistakes and being able to correct them. There is nothing better than being able to correct your mistakes after you have made them. It means that after a person makes a mistake, it is the best thing to be able to recognize and correct the mistake.

I feel happy when I hear it. When you hear others criticizing your shortcomings or mistakes, you feel welcome and happy. Refers to accepting opinions humbly.

If there are any, correct them, if not, encourage them. It refers to correcting the shortcomings and mistakes that others have pointed out to you. If there are any, correct them. If not, use them to remind yourself not to make the same mistakes.