Can you use LOA with anxiety and depression?

So I have severe anxiety and depression always have. I recently submitted a very important essay that I need to do well on. My anxiety is telling me that I’ve cheated on the exam, I’m going to get a zero and that I’ve basically failed. I have been listening to manifesting videos on YouTube and they are the only thing keeping me calm. Since yesterday, I have been journaling, positive affirmations and visualising doing well on the essay. But as soon as I stop doing these things all the awful thoughts creep back in. What can I do? Can I manifest to pass the essay and how can I keep the bad thoughts at bay