Modesty helps people to go forward.
When I was child, I was interested in math. I always read the math textbook and do a lot of exercises. So sometimes, I didn't like listening the math class. Because I have learned before my teacher taught us. At that time, my classmates always asked me some questions about the math. I could taught them how to solve these problem and this made me very proud of myself. However, my mother thought it is bad for me. She thought I was cocksure about the math. Maybe one day, I will meet big problem in math. But in my mind, it will never happen.
After a period of time, the math is becoming more and more difficult. Sometimes I also need to spend more time on solving the problem, nonetheless, I still thought I could handle the math and I didn't need to listen the math class. Finally, I got a bad score in my math final exam. The score made me cry the whole night.
After that, I think my mother is right. We cannot make ourselves over confidence. Modesty is very important for us. Over confidence always make us cannot see our shortcomings. So we must keep modesty all the time.