Learn to skim. You cannot possibly read everything carefully. Skim and pick out important bits to revisit, and spend time on the parts that are most relevant or useful to you. This is difficult in the early semesters because you will get a lot of pressure to engage deeply with everything that comes across your desk. YOU must prioritize - it's YOUR education.
I was super fortunate to have an advisor during my PhD who, when I would complain about getting pressure from other profs to do/study certain things, would simply remind me that it was my degree, not theirs. That reminder served me well (and still does) in terms of deciding how to spend my time in general.