He was more than willing to instruct me, and in my notebook he actually wrote in his own hand the three commandments he considered sufficient to make any firm prosper: 1. There's no need for a man to know how to work, but if he doesn't know how to make others work, he is doomed. (2) There is only one great regret: not having acted in one's own best interest. (3) In business, theory is useful, but it can be utilized only after the deal has been made.