A lot of great fortunes in the world have been made by owning a single wonderful business. If you understand the business, you don't need to own very many of them.
Each of us needs to withdraw from the cares which will not withdraw from us. We need hours of aimless wandering or spates of time sitting on park benches, observing the mysterious world of ants and the canopy of treetops.
My interest in science was always essentially limited to the study of principles.... That I have published so little is due to this same circumstance, as the great need to grasp principles has caused me to spend most of my time on fruitless pursuits.