Writing is tiring work

G K Chesterton writing to his friend, Bentley, not long after GK started his first job working for a publisher - Redway, mentioned in the letter. 

There is that confounded 'Picture of Tuesday' which I have been scribbling at the whole evening, and have at last got it presentable. This sounds like mere amusement, but, now that I have tried other kinds of hurry and bustle, I solemnly pledge myself to the opinion that there is no work so tiring as writing, that is, not for fun, but for publication. Other work has a repetition, a machinery, a reflex action about it somewhere, but to be on the stretch inventing things, making them out of nothing, making them as good as you can for a matter of four hours leaves me more inclined to lie down and read Dickens than I ever feel after nine hours' ramp at Redway's. The worst of it is that you always think the thing so bad, too, when you're in that state.

From Gilbert Keith Chesterton, by Maisie Ward, page 67.