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How do I improve my self-esteem?
Work on your negative self-talk.
Each time you remember something and cringe or insult yourself, you overwrite that memory with you feeling shitty about it. It's a terrible feedback mechanism.
Instead, laugh at your silly mistakes, celebrate your successes and failures, and forgive yourself.
It will take a long time to unwind the stuff you have done to yourself, but this is one technique you can just start doing - recognize when you are beating yourself up and do a little better.