What is the most difficult in English for you personally, dear teachers?

.  For me,  I forgette  words while speaking

The most difficult part is teaching students who are not aware of the English vocabulary, they would memorize the grammar methods but still unable to make a right phrase.

sleep of tongue.....and sometimes forgetting words....

Using the most appropriate verb at the right place.

Avoiding "slang" when speaking to non native english speakers.