In the United States, today is President's Day, in commemoration of the birthdays of George Washington, the first president (who was born February 22, 1732), and Abraham Lincoln, the 16th president (whose birthday was February 12, 1809). From what I've read, their temperaments and lives were at opposite ends of the spectrum.
Washington was happy, outgoing, friendly, stable, and energetic. (Actually I'm linking to a site whether they suggest that Washington would have been an ESFJ according to the Myers Briggs Personality Test. How amusing is this?)
But Lincoln's depressions were legion, and as far as I can tell, his behavior would seem to be bipolar. Robert L. Wilson, who served in the legislature with Lincoln, wrote in 1836, "In a conversation with him...he told me that although he appeared to enjoy life rapturously, still he was the victim of terrible melancholy. He sought company, and indulged in fun and hilarity without restraint, or stint as to time. Still when by himself, he told me that he was so overcome with mental depression, that he never dare carry a knife in his pocket."
The most famous quote attributed to Lincoln about his "melancholy" can be found in a letter he wrote in 1841 to John T. Stuart, his first law partner, describing his mood after he broke his engagement to Mary Todd, whom he later married.
"I am now the most miserable man living," he writes. "If what I feel were equally distributed to the whole human family, there would not be one cheerful face on the earth. Whether I shall ever be better I can not tell; I awfully forebode I shall not. To remain as I am is impossible; I must die or be better, it appears to me."
And William Herndon, Lincoln's third law partner, wrote, "He was a sad-looking man; his melancholy dripped from him as he walked. His apparent gloom impressed his friends, and created sympathy for him - one means of his great success. He was gloomy, abstracted, and joyous - rather humorous - by turns; but I do not think he knew what real joy was for many years... The perpetual look of sadness was his most prominent feature."
What's interesting to me is that I can't imagine any presidential candidate today being elected should he or she have the melancholic personality that Lincoln embodied. And yet, when we think of President Lincoln's legacy, his accomplishments were quite extraordinary...either despite his illness or because of it.
[I found all the Lincoln quotes on the Abraham Lincoln Research site.]