Sustainability is not a choice, it is a responsibility.

对称性是降低复杂性的概念（协同例程包括子例程）；到处寻找它。

I have a vivid memory of what happened， and it was not what I expected. I expected to be applauded for my cleverness and arithmetic skills. "Jeff， you're so smart. You had to have made some tricky estimates， figure out the number of minutes in a year and do some division." That's not what happened. Instead， my grandmother burst into tears. I sat in the backseat and did not know what to do. While my grandmother sat crying， my grandfather， who had been driving in silence， pulled over onto the shoulder of the highway. He got out of the car and came around and opened my door and waited for me to follow. Was I in trouble？ My grandfather was a highly intelligent， quiet man. He had never said a harsh word to me， and maybe this was to be the first time？ Or maybe he would ask that I get back in the car and apologize to my grandmother. I had no experience in this realm with my grandparents and no way to gauge what the consequences might be. We stopped beside the trailer. My grandfather looked at me， and after a bit of silence， he gently and calmly said， "Jeff， one day you'll understand that it's harder to be kind than clever."