Student or Learner
I've forgoten to learn english last night as usual I have.
In my opinion, it has to use past tense when an adverbial of time (in this case, "last time") was used. In addition, "as usual I have" is not better than "as I usually do."
Do you agree with me?
But I don't understand why "was used" is wrong while "as used" is right there.
Because "was used" can serve as the predicative, while "as used" is just an adverbial.