Think of a child. A child makes a lot of mistakes. Only after making mistakes and correcting them either by themselves or with the help of a teacher (adult), they do not repeat the mistake and learn. If we make the child feel bad for the mistake, they will not like it. Instead, we should be calm and reward the child for improving!

The same idea is true for adults learning a new language too. A good teacher sees mistakes in their students as something normal. If we do not make mistakes when learning a new language then we are doing something wrong! That's why do not be scared to make mistakes. If your teacher makes you feel bad for being wrong, they are not a good teacher!

Happy learning! :)