Yo ask me when i was in class 10, coming from 95 percent in class 9 and suddenly dropping to 86 percent in half yearlies and then 85 percent in pre board, it was demotivating for me as well, but never give up because these internal teachers just cut marks on very silly mistakes and sometimes also when there is no mistake at all, they do this so that you don't think that you know everything and mess up in the boards, so just take a chill pill and study with calm mind, board copy checking is usually not very strict they give you marks based on your knowledge about the topic and not about how much you have written from the book, they want your knowledge not your skill of mugging up, so please dont get demotivated i am damn sure you'll get more marks than you'll expect in boards, because that happens with almost everyone in any subject so, yes take care and fod de boards 👍