Learning should never be unpleasant. If it is, consider exploring supermemo.guru. It has many articles on learning, memory, sleep... and is maintained by one of the most knowledgeable people on the topics of learning. For this particular question, explore the articles on toxic memories, to see why some people experience anxiety before learning.
I am not in ANY way affiliated with this site, I just read it often and the articles have helped me more than I can describe in words.
I second it. The site looks a bit old and the articles are quite long, giving it that rambling madman feel. But it's all good stuff by a qualified researcher.
I am not in ANY way affiliated with this site, I just read it often and the articles have helped me more than I can describe in words.