Laszlo from Hungary: There is a rule: "we almost never use the countinous tense with some verbs. eg: be". But there is a sentence in this lesson: "You are being too negative." Is it an exception? Why?
Answer: You are correct that we generally do not use 'state' verbs (be, like, feel, hate, etc) in the -ing form, because they are not describing actions.
However, some state verbs ('be' and 'think', for example) can sometimes be used as action verbs, depending on the meaning. For example: I am already thinking about my holiday or I am being nice to you because you helped me yesterday.
Think of this as more casual language (some teachers do not think it is good grammar). Most native speakers use this language, so you will hear it quite a lot.