Have you read The Now Habit by Neil Fiore? It's primarily talking about procrastination, but there were a few things I found useful to apply to my own workaholic tendencies.
He talks about an 'unschedule' - where you schedule all the fun stuff, and work has to fit around that. I've found imposing those kind of limits on work to be very helpful (i.e. no work between X and X or after X). But the crucial piece of the puzzle is to plan what I'm going to do with the non-work time, for example, decide that between X and X I'm going to go for a walk to X. If I don't do that, I easily slip back into my default work mode.