Masayoshi Son, the billionaire founder and CEO of SoftBank, the Japanese media technology conglomerate, is often cast as a dreamer, financial engineer, and speculator. But his career — which has spanned the launch of the personal computer and internet, dotcom boom and bust, the rise of China, the global financial crisis, and the advent of artificial intelligence — offers eight key lessons for leaders. They include: turn adversity to advantage, find a way to persist, bridge east and west, seek mentors and mentees, go big or go home, don’t let love outweigh logic, beware mercenaries, and focus on the future.