Enid Blyton said this quote
“ I wonder where you got that idea from? I mean, the idea that it's feeble to change your mind once it's made up. That's a wrong idea, you know. Make up your mind about things, by all means - but if something happens to show that you are wrong, then it is feeble not to change your mind, Elizabeth. Only the strongest people have the pluck to change their minds, and say so, if they see they have been wrong in their ideas. ”