Buying tools: Start by buying the absolute cheapest tools you can find. Upgrade the ones you use a lot. If you wind up using some tool for a job， buy the very best you can afford.
原文英文：The most merciful thing in the world， I think， is the inability of the human mind to correlate all its contents. We live on a placid island of ignorance in the midst of black seas of infinity， and it was not meant that we should voyage far.
