Energy > Time

Having personal energy to do what you want to do is more important than time.  I can demonstrate this simplistically.  Suppose you tell me you don't have time for something. Then I suggest that you get up two hours earlier, or wake your self up at 3 a.m. to work for two hours. Or that you simply devoted two hours after dinner to something.  You will likely say you are too tired to take my suggestion.

I am not recommending less sleep, or any other biologically questionable solution.  What I am saying is that your problem is likely to be energy, not time. Writing intensely on your project for 2 hours requires sustained, concentrated energetic work. It is likely that you don't achieve that often enough.

Some likely causes:

*The research is really your last priority. You do everything else before that. Then, surprise surprise, when you finally turn to it you are at a low energy part of the day--a time better spent in activities that don't require that amount of energy.

*Generally, you are living your life in a way that does not maximize energy.

Now it could really be that you are too busy, that your busy life does not allow you to do research.  In this case you must re-prioritize.  Look at your work-week analytically.  For me, for example, I find that I need up to one hour to prepare one hour of class and otherwise attend to everything having to do with that class. I teach five hours a week, so I need 10 hours of prep / grading / administration, so that is 15.  That leaves me with 25 hours a week for everything else.  Service is supposed to be 4 hours, so now I have 21. I should be able to fit in 10 hours of writing, including blogging, and 11 of reading, working 40 hours a week and still taking weekends and evenings off. If I really did this all the tie, I would be publishing much more than I do, even. But I am a low energy person....