While staring down the pointy end of the semester and exams looming large, it can be tempting to just go hell bent for leather to try and cram as much studying and as much study time  in as possible. But really, you will be most productive, if you work to your energy levels. If you’re feeling tired or unwell or just couldn’t be stuffed, don’t force yourself. You will end up feeling worse and ultimately you won’t retain much knowledge. If you’re feeling tired, do a small amount of study then take a break. If you’re feeling energised, allocate a more substantial block of study time to suit your levels. Work with, not against your energy levels and the results will speak for themselves.