Since I was a child, my mouth has caused me trouble. I’m not a bad person. I have a hard time learning when to keep my mouth closed.

My mom has told me again and again, “Robert, your constant _________ words are hurting me. If you continued to be this rude, you will get into big trouble.”

It’s been a problem at school several times too when teachers have told me something I didn’t want to hear. I used to feel it was my duty to _________ myself.

One day in English class I was working on my homework until I heard a classmate_________ behind me. It was Nathaniel, who liked doing that as usual.

At first, I said very politely, “Nathaniel, would you please be quiet?”

However, Nathaniel continued talking to himself. I quickly _________ “Nathaniel, shut up!”

For the next five minutes, we threw hurtful words back and forth at each other.

I knew these words would make him _________. It would hurt his feelings and shut him up.

What I said filled him with anger. He tried to reach over my seat and catch me as he shouted, “That’s it! That’s it!”

_________ at what he was doing, I sat back in my seat. I had never seen Nathaniel act like this before.

Later on, we were taken to the headmaster’s office. There, Mr. Black, our English teacher, told us to _________the matter. It wasn’t until then that I finally found that when I hurt someone physically（身体上）, the wounds eventually heal（愈合）. But when I hurt them with my _________ sometimes the pain never goes away.

At the end of the discussion, I said sorry to Nathaniel.

When I went back to my room, I lost myself into _________ how often and how much what I said hurt others. It’s at that time that I realized I should keep my __________ closed just before I threw hurtful words. I hope my mouth won’t cause me any trouble.

Monarch butterflies from eastern Canada make the most amazing journey in the insect world. Each year, this butterfly travels about 3000 miles to its winter home in central Mexico. How can it fly so far? And why does it make this long and dangerous trip? Scientists still don’t have an answer.

For many years, people in Mexico wondered where the orange-and-black butterflies came from every winter. Then, in 1937, a scientist started to follow and study the butterflies. For the next 20 years, he discovered that one butterfly started its journey in Canada. Four months later, it arrived in Mexico.

The length of the butterflies find their way back to the same place? Another amazing thing is that the butterflies always return to the same area in central Mexico.

How do the butterflies find their way back to the same place? This is an interesting question because only every fourth generation（代）makes the trip south. In other words, the butterfly that travels to Mexico this year is the great-great-grandchild of the butterfly that traveled there last year.

Each year, four generations of a Monarch butterfly family are born. Each generation of the family has a very different life. The first generation is born in the south in late April. It slowly moves north, reproduces（繁衍）, and then dies. On the trip north, two more generations are born, reproduce, and die. Each of these generations of butterflies is born. This generation has a much longer life. It lives for about eight months. This generation of butterflies makes the amazing journey back to the winter home of its great-great-grandparents. The butterflies spend the winter there, and in the spring they reproduce and then die. Their offspring will be the first generation of the next circle of life.

Today, people are still studying the Monarch butterfly. But they are not clear about everything.

Imagine this. There's an apple and a piece of cake on a table. Which one would you like? The delicious cake or the healthy apple? A bestseller, Willpower: Rediscovering Our Greatest Strength, suggests that willpower(意志力)is the ability to make decisions that are better for us in the long term, rather than in the short term.

Here is a famous experiment in the book: The Marshmallow Test. In 1972, Professor Walter Mischel tested the willpower of 600 four-year-olds to six-year-olds. In the experiment, each child was left alone in a room for fifteen minutes with a marshmallow(棉花软糖）on a table in front of them. They were given two choices: they could either eat it or, if they waited fifteen minutes, they'd be given a second one(and then they could eat both).

So, what did the kids do? Well, as you can imagine, 70% ate the first marshmallow within the fifteen minutes. But the other 30% showed willpower—they controlled themselves and waited for the second marshmallow. But then Mischel discovered something really interesting. Twenty years later, he got in touch with the children, who, by then, were in their early twenties. And he found that those who'd shown strong willpower were getting better marks at university and were more popular.

Willpower is like a muscle（肌肉), and the more you exercise it, the stronger it gets.

So, if you do daily "self-control exercises", such as making your bed or brushing your teeth, you'll improve your overall willpower. And daily willpower exercises will help you with those bigger goals, such as studying for an exam or training for a marathon.

Be careful though. Just like any muscle, your "willpower muscle" can get tired. If you've had to do lots of things that require willpower, take a break or give yourself a treat.

That way, you’ll build up your willpower again.

And one last thing, the writer mentions people who learn foreign languages usually have a lot of willpower. So, congratulations!