How to be efficient as a graduate student juggling classes, TA and research? I am a first year PhD student, and it's the fourth week of school. I am taking two classes, doing one grad class TA and doing a lab rotation. I am in Electrical Engineering (Controls and DSP). 

I start my day thinking- "I'll go to class from 10 am to 12 pm, solve 5 homework problems from 1 pm- 3 pm, do some TA work from 4 pm to 6 pm, and read a bunch of papers from 7 pm to 9 pm, then cook and sleep. How optimistic. 

In reality, when I start the homework problems at 1 pm, I end up having to read a bunch of textbooks to understand stuff in it (I'm doing Convex Analysis), and by the time 3 pm rolls around, I have finished only one problem. Feeling discouraged, I keep at this homework, vowing to stop only when I'm done with my quota of 5. My efficiency starts to drop severely after a few hours, but since I'm in school with my laptop and stuff, I can't go anywhere to 'relax', so I just keep sitting and start redditing or something. And then my concentration further drops when I try to resume real work. This goes on, I miss dinner, I sleep late, and the efficiency just plummets through the week. 

My past couple of weeks have been so inefficient, I want to do something about it before it's too late. 

In short, my question is, when your work is way too difficult to achieve your goal of the day in your allotted time, do you switch work, or do you keep going? I have always believed that output is more important than input, that is, putting in two hours for each task without achieving much in anything is not as good as putting in, say, eight hours for just one and finishing something in it nicely. However, this strategy of mine is failing me for the first time in my life, because even if I put in eight hours, I am not able to finish anything. The work is so difficult. I'm not complaining, just really need guidance.
When your work is way too difficult to achieve your goal of the day in your allotted time


... get used to it. If you are an interesting person doing interesting things, there is never going to be enough time for all the things you want to do. And as soon as the work you're doing now starts to get easier for you, you'll get new, more challenging responsibilities :)

You won't be able to manage your time more effectively until you get a little better at estimating how long things will take, so start there. It's pretty common to underestimate how long things will take - try quadrupling your initial estimate, and see where that gets you.

When you can judge more accurately how long things will take, you will be in a better position to manage your commitments. Once you realize that your homework takes you 8 hours, not 2, you will be able to plan your week accordingly, without feeling guilty when you invariably have to drop something else in order to do your homework properly.

In the meantime, 


  Keep forgiving yourself and keep working


That's from this answer by Piotr Migdal, which I highly recommend you read.


  I miss dinner, I sleep late, and the efficiency just plummets through the week.


You don't need me to tell you the answer to this one. Take care of yourself. For more details, see How to prevent physical/psychological health side effects of workaholism in academia and research?.


  do you switch work, or do you keep going?


It helps to have tasks you can work on when you are low on intellectual energy, but that are still more productive than staring at reddit. Here's a list of ways to procrastinate productively. 

Ultimately, though, if you need to take a break to recharge, just do it - then you'll get back to work and be much more effective.