So, you’re in class and the teacher calls on you to read some long passage that is full of ridiculously obscure characters. And you were traveling all weekend so you didn’t preview this lesson. And this happens to be the teacher who has publicly derided you multiple times for having bad pronunciation. Feeling kinda stressed? Guess what that does to your language ability?
Yup, it sends it into a nosedive. Suddenly you can barely squeak out “好的” in response to being called on, let alone read the passage well.
This is your affective filter at work. Pop over to Taking Route where I write a longer explanation with my own embarrassing example of being totally flustered when trying to buy band-aids. There are some helpful links at the end of the TR post if you’d like to learn more about combatting this language learner’s challenge.