There are also people who cannot take it - sure they can keep going but it tired them out and leaves them good for nothing but work and relaxation, nothing creative or fun or any of the things they really like doing. Perhaps it is because they like making things that they burn out, their outlet for proper relaxation not being accessible to them any more in any real, meaningful manner.
Either way, I've come to the conclusion that I fall into the latter category. It's not helping that on top of the workload I've also been moving house. I can feel some sort of breakdown on the way, it might be a pissy fit or it might be a full on "fuck this job" screaming match. Whatever, it's starting to depress me in a fairly serious manner and I think I need a way to avoid it.