I've had a similar problem in learning large swathes of complex material. I found myself often tired and easily distracted. Modafinil helped with the tiredness

I've had a similar problem in learning large swathes of complex material. I found myself often tired and easily distracted. Modafinil helped with the tiredness and kept me more intensely focused than I normally would be. Flashcards in question/answer format helped with making sure I remembered the core facts of what I was trying to learn. Not sure if this will help but it worked for me somewhat.