Here is one strategy which I'd like to share with you:
Say you have a whole day off. When you get up in the morning, grab a piece of paper or a text file, and write down a sequence that lets you have some enjoyable time off, but still combos nicely into the productive thing.
Example:
I'll game for an hour or two in the morning, then I'll head out and get breakfast and go for a walk, and then I'll return and study for an hour or two
The exact details and the order isn't so important, but in my experience, it feels quite nice to enjoy some "fully allowed" leisure time. And the productive time is enjoyable as well, since it's a change of pace, and it gives your day some purpose/structure