I am Wilson. My sister and I spent our summer holidays with our uncle this year. He is a geologist (地质学家) and loves to collect stones.

One day, he bought us two backpacks and asked us to go to the mountain with him. We walked the whole day. Every now and then he put stones in our backpacks. To our surprise, he also took some stones out from them. But we thought he had just found better stones.

    When we returned to the house, we were very tired. The backpacks were so heavy that we felt great relief (轻松) when we took them off. Yet our uncle's backpack was half empty.

    “Why did you give us so many stones?” we asked.

    “I didn't. You did,” he said. “You didn't know it, but I gave you a little attitude test today. I listened to every word you said. Whenever you were complaining, I added a stone to your backpacks. Whenever you talked about something with positive thinking, I took out a stone. And now look at your backpacks.”

    Our backpacks were full of stones.

   “Your negative thoughts are just like stones. You carrythemin your mind just like those stones in your backpacks. The more negative thoughts you have, the heavier your mind will be,” said our uncle.

    With great love, our uncle taught us one of the most important lessons in life — the power of the attitude.