"The best and most beautiful things in the world cannot be seen or even touched - they must be felt with the heart."
The best banking service is invisible but always available.
The trick is to pay attention to what's happening around you and to keep writing.
解析:教导学生,不到他想弄明白而不得的时候,不去开导他;不到他想出来却说不出来的时候,不去启发他。