什么道理?

Integrated design is finally due today. Now there's only dissertation left! I am so out of energy so have a song:



I particularly like these lines:

多少人在追寻那解不开的问题
多少人在深夜里无奈地叹息
多少人的眼泪在无言中抹去
亲爱的母亲这是什么道理