I have experienced this last month and it continues when I met my supervisor last week. I just don't understand the sudden change. It happened four days before I should submit my upgrading chapter. Previously, he had been so nice and even forward the relevant articles to me. A week before, he said that my progress is okey and I don't have to worry. However, lately, he always undermine me, saying that I'm average and he could see that even I manage to pass the upgrading session, he has doubt whether I manage to complete this PhD. For the time being, I try to gain my confidence and prepare for the upgrading. However, I would like to seek your opinion, what is the best thing I should do? (I'm thinking of change the supervisor actually since what he mentioned to me is not promising)