对一切数据进行冗余备份，至少要有一个物理硬盘备份和一个云端备份。每个备份都要多于一个。想想要是你弄丢了所有数据、照片、笔记，得花多少钱来找回它们？与遗憾相比，备份很便宜。
Be a pro. Back up your back up. Have at least one physical backup and one backup in the cloud. Have more than one of each. How much would you pay to retrieve all your data， photos， notes， if you lost them？ Backups are cheap compared to regrets.
Common sense tells us that performance comes and goes, but costs go on forever.
To understand psychology, observe behavior in its natural context.
——《在广州岭南学生欢迎会的演说》（1923年12月21日）
I think that the thing that makes mathematics worthwhile is the fact that it has this incredible structure that you can explore and discover.