graduate school - How to get back on track after falling behind

I'm a first year master student currently taking courses on the second semester. For the most part I did pretty good on the first semester except that I got behind in one course which is specially demanding and hard.

Now I'm taking the equivalent amount of work as before plus I'm trying to finish my assignments for the other class in order to get my grade. And I'm also collaborating in a research project which I wasn't doing last semester.

I'm having a hard time trying to manage my time in order to accomplish everything. As I don't want to get behind in another course I try to be on top of what I'm seeing in class. However I find that this consumes a lot more time than I expected and I never accomplish the goals I set for the day.

As an example, if I have some class the next day I try to really understand everything we saw the previous meeting, and by the time I manage to do that (if I do), there is only about 3 hours left to do everything else. In a normal day I expend all the time doing my "academic stuff" and I only stop for eating and sleeping. Where the sleeping time could vary from 0 to 6 hours depending if I feel I'm getting too far behind or if I managed to finish all I wanted for that day (rare). I have to admit that I always try to get the most miniscule detail and expend a great deal of time thinking how to go from point A to point B on the text which in some sense is a pedantic attitude. However, I find that if I don't do this, then the ideas are very shaky (there are holes in my understanding) and I tend to forget those very easily, which is not good for doing exercises or taking an exam.

I have tried to split the day in blocks and only expend a fixed amount of time doing an specific task. However, this way I feel I go so slow that I'm not accomplishing anything. So basically what I end up doing is working nonstop in one task (which can take more than one day) and then try to compensate for the other tasks I didn't do by cutting sleeping time or further delaying other work.

I sometimes think that if I'm working that hard at this level, I have no chance of getting a PhD or continuing in academia. I see that some of my peers have time to have fun, go out and still get good grades while I barely have time to enjoy a meal. I also get good grades (I have to in order to keep my scholarship) but I feel that the effort I'm putting is too much for the reward (not exceptionally good grades).