To anyone who is not an artist it must seem rather strange that Degas who could do anything — for whom setting down what he saw presented no difficulties at all — should have continued to draw the same poses year after year — often, it would seem, with increasing difficulty. Just as a classical dancer repeats the same movements again and again, in order to achieve a greater perfection of line and balance, so Degas repeats the same motifs, it was one of the things that gave him so much sympathy with dancers. He was continually struggling to achieve an idea of perfect form, but this did not prevent him looking for the truth in what might seem an artificial situation.

Ch. 13: Degas - The Romantic Rebellion (1973)