I think you'll have to find a way to enjoy your research. I remember reading a blog post by a programmer who'd wake up at 5am everyday to code for two hours. He wrote -
Enjoying the work is key
It's 5am and I will be also putting in a full day's work afterwards. Not being stressed out or frustrated during this time is essential. I ensure this by working on truly personal projects that interest me and I have complete control over. I'm only two weeks in but so far no signs of getting worn out, in fact quite the opposite. It's been pretty invigorating.
And then this interview of a guy building a PHP webframework -
I don’t have any other side projects right now. Laravel consumes most of my development free time and I only work on the framework after my wife and kids go to bed. So my development time on Laravel starts at about 10pm and wraps up at midnight, allowing me to work on it for a couple of hours per day without detriment to friends and family.
Later on he advises people to enjoy whatever they are working on.
So key here is to be excited about what extra work you do. What is your research area? Does that excite you, or are there parts of it which are interesting? Maybe you could try building something using your research, something that would be enjoyable to build.
Pick a time, and stick to it. Find a way to make your research exciting.
And try to eat well and keep yourself fit - 10 hour work day + a couple of hours studying will take its toll on you.
I guess that is about it.