G.K. Chesterton:
The artistic temperament is a disease that afflicts amateurs. It is a disease which arises from men not having sufficient power of expression to utter and get rid of the element of art in their being... Artists of a large and wholesome vitality get rid of their art easily, as they breathe easily, or perspire easily. But in artists of less force, the thing becomes a pressure, and produces a definite pain, which is called the artistic temperament. Thus, very great artists are able to be ordinary men... There are many real tragedies of the artistic temperament, tragedies of vanity or violence or fear. But the great tragedy of the artistic temperament is that it cannot produce any art....

It need hardly be said that this is the real explanation of the thing which has puzzled so many dilettante critics, the problem of the extreme ordinariness of the behaviour of so many great geniuses in history. Their behaviour was so ordinary that it was not recorded; hence it was so ordinary that it seemed mysterious. Hence people say that Bacon wrote Shakespeare. The modern artistic temperament cannot understand how a man who could write such lyrics as Shakespeare wrote, could be as keen as Shakespeare was on business transactions in a little town in Warwickshire. The explanation is simple enough; it is that Shakespeare had a real lyrical impulse, wrote a real lyric, and so got rid of the impulse and went about his business. Being an artist did not prevent him from being an ordinary man, any more than being a sleeper at night or being a diner at dinner prevented him from being an ordinary man.

from Daniel Mitsui's The Lion and the Cardinal http://www.danielmitsui.com/hieronymus/