Uber CEO 's advice: pick the right person to work for. "Environments are unpredictable, but people usually stay successful. Look at Elon — he's succeeded in so many different areas. And that's true for really exceptional people. Exceptional people stay exceptional, regardless of the environment." "If you pick a company, or you pick a position, that can change. That can go the wrong way. If you pick the right person, not only do you get to learn from them, but they usually move up in the…