The idea of “planning” a career is now garbage. You can only improvise one. Listening dutifully to old-economy career counselor types at ages 18 and 22 and “first layoff” is now the stupidest thing you can do. To a large extent a) your career picks you, not vice-versa, and b) It isn’t about what you want to do, but which one of the things you like doing achieves a “product-market fit” with the labor market.
(Most of the post is about entrepreneur-ing and startups; skip to the bottom for the "Your Life as a Lean Startup" section.)