Jensen Huang says he was happier in his 20s than he is now. The reason is not what you think. He wasn't happier because NVIDIA was smaller, or because the work was simpler, or because he had less money on the line. He was happier because he was ignorant of how impossible the thing he was attempting actually was. His exact phrasing: he thought his 20s were happier, and looking back, the reason was that he didn't know enough to be afraid. If he had understood the real probability of building…