The key is to get some sleep, and to try finding something that motivates you for learning. It can be independence, accomplishment,knowledge, anything. Attention is the most important thing. The good technique is to think of every word and its meaning, then on the meaning of the entire sentence, paragraph, page, lesson. Also, focusing on keywords helps. If you find confusing words that associate you to something else, write them down, and don't read them until you have the entire lesson in your mind. The next step is to ask questions to yourself and to answer as if you are an expert of the area, confident, loud and clear. Study for the knowledge, not to get approval from the professor.