Stephen Budiansky admires FDR's temperament: 

The more I study history and human nature the more I find myself convinced that (all of the political pundits and business schools and self-help gurus notwithstanding) the essential qualities of leadership simply cannot be learned; I'm not saying they are genetic it's hard not to believe that part of FDR's remarkable character, particularly his extraordinary blend of self-confidence, equanimity under pressure, and fellow-feeling, owed much to his personal struggles with polio but that they do stem from intrinsic temperament and character more than any other factor.