Dickerson explains why it's so critical for the job:
A president’s temperament is his most important quality and it is the hardest to measure in the candidates who desire the office. It is at the heart of all the other key attributes. A president can’t ignore his critics unless he has a reliable sense of himself. He can’t make durable decisions unless he has strong values in which he roots them. The political game requires patience, and a willingness to ignore one’s emotions. He can’t adapt unless he has the emotional maturity to accept the fallout.