Lesson in life:

A wise man sat in the audience and cracked a joke. Everybody laughs like crazy. 

After a moment, he cracked the same joke again.

This time, less people laughed.

He cracked the same joke again and again.

When there is no laughter in the crowd.

He smiled and said:

You can't laugh at the same joke again and again,

but why do you keep crying over the same thing over and over again?