"Hope is the thing with feathers that perches in the soul, and sings the tune without the words, and never stops at all."

Life lessons will be presented to you in the order they are needed. Everything you need to master the lesson is within you. Once you have truly learned a lesson， you will be presented with the next one. If you are alive， that means you still have lessons to learn.

软件系统最重要的方面是它满足用户需求的能力。