Alan Watts has a great metaphor for keeping your balance. He says it's like riding a bike. When you start falling on one side, your natural instinct is to turn in the other direction. Of course, if you do that, you fall very fast. The key to staying upright on a bike is to turn in the direction that you're falling into.
The metaphor translates very well to keeping your balance as a human being - go into the direction that you're falling into. In other words, if you find that your body and mind and subconscious is telling you, "I don't want to do X anymore!" don't try to force yourself to do it anymore. And if you find that the message is "I really want to do X" follow it.
Of course, to keep your balance on a bike, you need to pay attention to what your senses are telling you. And to keep your balance in life, you need to pay attention to what your subconscious is telling you.
There's a balance to be sure, and there's some learning about yourself that is necessary. For instance, there's a critical difference between the feelings "I'm burning out and do not want to do this task" and "This task is boring".
It's possible you're feeling lazy; it's also possible that you're closer to burnout than you realize and that is your brain/body telling you that you need a break. Only you can decide which is which. There are consequences to being wrong either way, but, well, c'est la vie, non?
I've had some success maintaining some longish work hours, even under the American-style "vacations are for people who live in other countries and don't have babies" regime, for a very long time with this basic approach because only rarely will I force it, and when I have to for some reason I always budget some days that I will simply take off from computing entirely.
"He says it's like riding a bike. When you start falling on one side, your natural instinct is to turn in the other direction."
No it isn't. Not at all. My natural instinct is to steer in the direction of the fall. I can't imagine this even being remotely true for anyone else, either.
I very distinctly remember my first instinct when learning how to ride a bike was to turn opposite of the fall. The same could be said for when I first learned how to drive on snow. It only takes a couple bad falls before your instinct changes with bikes and cars, but I don't think people make that realization with burn out.
I think it was initially a bad analogy; he probably meant something along the lines of noticing you're about to fall off a ledge of sorts. In that situation, you would stick out a limb to keep your center of gravity on solid ground, not lean further away :)
The metaphor translates very well to keeping your balance as a human being - go into the direction that you're falling into. In other words, if you find that your body and mind and subconscious is telling you, "I don't want to do X anymore!" don't try to force yourself to do it anymore. And if you find that the message is "I really want to do X" follow it.
Of course, to keep your balance on a bike, you need to pay attention to what your senses are telling you. And to keep your balance in life, you need to pay attention to what your subconscious is telling you.