I was amful, because we had some differences in requirements with our customer. we were probably wrong in understanding requirements. Tommorrow we will talk them with our customer detailedly, I hope that there is a good result. When I was down in spirits, I took up a book and read it. the book named good students, good methodologies is very good. it is writen by a teacher named Wei Susheng. There are many studying methods in this book. After reading this book, I felt very well. So please read a good book if you don't feel well.