I have a love/hate relationship with Leo Tolstoy. I love his fiction, and for that reason keep feeling compelled to learn more about his life, but then am driven away by his faults. I should stay away from Tolstoy biographies and just read his novels.
In any event, for happiness-project purposes, Tolstoy is particularly fascinating - both because he wrote so extensively about happiness and because he made and broke so many resolutions himself. Spectacularly.
In Henri Troyat's biography, Tolstoy, which I never did finish, because I found Tolstoy so maddening, Troyat includes an excerpt from Tolstoy's "Rules of Life." Tolstoy wrote these rules when he was eighteen years old.