I did it that way the first block of each semester-- each time with some professor or friend's voice in my head. Each time I tried, I had less time to study, sleep, and exercise. I performed adequately, but not at my best, during exams.
What was wrong? I had not taken ownership of the class and of the material, of my learning style, and of all of the options available to me.
Each semester, my best blocks were those in which I attended NO classes physically, but used my time to read the course book and stream lectures online instead. During these blocks, I was well rested, exercised daily, and cooked my own food.
Taking ownership of the material meant waking up in the morning not because of a class but because of my responsibility. It meant actively studying in the library with a friend instead of passively sitting in the lecture hall. It meant understanding that rest and cognitive ability were paramount to success.
This was difficult. It was difficult because the only measure of success is just that; not martyrdom, not suffering-- only mastery.