Imagine, if you will, that your best friend talked to you the way you [silently] talk to yourself in your most self-critical moments.
Imagine, if you will, that this friend has no confidence in you, doesn’t think you can amount to anything, thinks that you are okay being average.
Would you keep such a person as your friend?
Then why do you talk to yourself the way you do if you can’t stand anyone talking to you that way?
I hope that, pretty quickly, you will get a new best friend.
PS: The two boys in the picture are best friends who first met at an orphanage in Mozambique when they were young. They then separated when they were adopted. Interestingly, the boys were adopted by families both from Arizona [USA] and living just less than two miles from each other. Because of that, the boys met again. It means they talk to each other as best friends should. Do the same when you talk to yourself, be your best friend.