There is a lecture I give to many students one-on-one every semester when they get into trouble. It is about how to read a math book, i.e. basic study skills. I recommend it for all my students. How to read a math book.
A more recent lecture I have to give to lots of students is the one about dealing with being accident prone.
An alternative, and much longer, version, which I have not read myself, might be useful.
Something well worth looking at is the Mathematics Survival Guide.
This could explain a lot: Why Students Think They Understand - When They Don't.
A series of 6 videos on how to study