I don't think he's saying to just take a bumble-along happy go lucky approach, with no rigor, training or mental discipline, but that you can't "sit down and invent things" most of the time. Sure, you can point yourself in a direction, but even then, you have to try, fiddle, experiment, and calibrate as you go along, and you might even then arrive somewhere that you didn't set out to go, if you're well placed to grab opportunities.