[–] divbit link

>In a bewildering act of vandalism, Manet slashed the picture right through the profiled face of his wife. Smee suggests that Manet felt Degas had portrayed him as overcome by ennui, boredom, indifference, even contempt. The cut was the psychological equivalent of Manet stabbing Degas.

Judging from the article, rivalries sound like they lead to fairly unhealthy behavior, also people have different strengths and weaknesses, so why measure yourself based on someone else.