We all make mistakes, so we need to learn to accept them as a fact of life. Making a genuine mistake does not make you any less of a person.
If anyone gives you an unnecessarily stressful time about making a mistake, remember they will have made just as many mistakes as you, if not more. The question 'May I congratulate you on never having made a mistake in your life?' is a useful answer here (just not to your teacher)!
Never making a mistake means never living life to the full.
More useful lessons are learnt from mistakes than from successes.
Children learn to walk because they get up when they fall, not because they stay down.
Repeat each morning that to risk failure is to court success.