A Lesson in Life:

A wise man sat in the audience and cracked a joke. 
Everybody laughs like crazy.
After a moment, he cracks the same joke again.
This time, less people laugh.
He cracked the same joke again and again.
When there was no laughter in the crowd,
he smiled and said:

"You won't laugh at the same joke again and again,
but why do you keep crying about the same thing again and again?"