It is now 16 years since my first book was published, & abt 21 years since I started publishing articles in the magazines. Throughout that time there has literally been not one day in which I did not feel that I was idling, that I was behind with the current job, & that my total output was miserably small. Even at the periods when I was working 10 hours a day on a book, or turning out 4 or 5 articles a week, I have never been able to get away from this neurotic feeling, that I was wasting time. I can never get any sense of achievement out of the work that is actually in progress, because it always goes slower than I intend, & in any case I feel that a book or even an article does not exist until it is finished. But as soon as a book is finished, I begin, actually from the next day, worrying that the next one is not begun, & am haunted with the fear that there will never be a next one—that my impulse is exhausted for good & all. If I look back & count up the actual amount that I have written, then I see that my output has been respectable: but this does not reassure me, because it simply gives me the feeling that I once had an industriousness & a fertility which I have now lost.
— George Orwell, 1949 notebook entry (via)