Imagine you are standing on the 70th floor of the Empire State Building, gazing at the cityscape. Suddenly a rather large man brusquely pushes past you, wrenches the window open and announces his intention to jump.
You yell out, "Stop! Don't do it!"
The six-foot-five figure turns to you and menacingly says, "Try to stop me and I'll take you with me!"
"Umm... No problem, sir. Have a safe trip. Any last words?"
"Let me tell you my troubles," he says. "My wife left me, my kids won't talk to me, I lost my job and my pet turtle died. So why should I go on living?"
Suddenly you have a flash of inspiration.
"Sir, close your eyes for a minute and imagine that you are blind. No colors, no sights of children playing, no fields of flowers, no sunset. Now imagine that suddenly there's a miracle. You open your eyes and your vision is restored! Are you going to jump? Or will you stick around for a week to enjoy the sights?"
"I'll stay for a week."
"But what happened to all the troubles?"
"I guess they're not so bad. I can see!"
"Well your eyesight is worth at least five million dollars. You're a rich man!"
If you really appreciate your eyesight, the other pains are insignificant. But if you take it all for granted, then nothing in life will ever truly give you joy.