One day, the teacher wrote on the board:
When he finished, he looked at the students, and everyone laughed at him. The first and easiest task was not correct.
The teacher said: "I wrote the first task incorrectly because I wanted to teach you something important: tomorrow the world will be cruel to you, as you are today towards me.
As you can see, I wrote nine correct tasks, but none of you paid attention to it. You all laughed and criticized me for just one mistake I made.
This was your lesson: 'The world will never appreciate the good things you have done a million times, but will criticize one mistake you've made.'