Three juggling balls and one more

Once upon a time, there lived a boy. His dream was to perform in a circus. On his birthday, his parents got him three juggling balls and one more. The boy got really excited and threw himself into learning juggling.

He started with three juggling balls. He was trying to juggle as soon as he woke up. He was trying to juggle right after breakfast. He was practicing on his way to school. He was throwing his juggling balls during the breaks between classes, he was getting better on the way home. And before going to bed he was juggling. He was juggling three balls! And they didn’t fall on the floor. Almost never. Only occasionally one ball would fall. He was juggling three balls!
But there was one more ball. Sometimes the boy looked at that ball. It was lying in the corner of his desk. He couldn’t understand how it was possible to juggle one more together with the three. It just didn’t make any sense. He heard that it’s possible to juggle three and one more. He even saw a video of someone doing it. But the boy really doubted he had what it takes to juggle three balls and one more.

So, the extra ball was lying there, in the corner of the table, getting dustier and dustier. And the boy stopped noticing it eventually and forgot about it…
Until his math class many months later. The boy was sitting in class, struggling with a challenging problem. He was good at math, but this problem was especially difficult and the boy didn’t even know how to approach it. He was sitting next to a girl, who wasn’t a good student, as far as the boy knew, but her hand was up in the air - she figured out how to solve the challenging problem, first in the class! The boy was puzzled and awestruck. He started paying attention to the girl.
The boy suddenly realized that she could solve any math problem! Nothing seemed impossible for her - she could always figure it out! “Wow” - the boy thought - “If she is able to solve such difficult problems, how hard can it be to learn to juggle four balls?”
The boy came home, washed his fourth ball, and threw himself into learning to juggle three balls and one more.

He was trying to learn to juggle the first thing in the morning. And right after breakfast. And on his way to school. And during the breaks between classes. And on the way home, and before going to bed.
Until one day he got it! He was juggling four balls! And they didn’t fall on the floor. Almost never. Maybe only occasionally one ball would fall. But he was juggling four balls!!!

So happy was the boy, so grateful to the girl who inspired him, that one day when they were sitting and waiting for the class to start, the boy told her how impressed he was with her ability to solve crazy math problems and how juggling the fourth ball seemed not so impossible to master, compared to math, and how he mastered it thanks to her.

When the girl heard this she started laughing.

“Why are you laughing?” the boy asked, puzzled.
“You see,” the girl said, still laughing, “a few months ago you started coming to school with three juggling balls. And you couldn’t juggle at all at the time. But you kept going, kept trying, every day, every free minute. At that time I didn’t really know math. In fact I thought I was too stupid for math. But seeing you not giving up, even if it was hard for you, and eventually mastering juggling got me thinking - maybe it is possible to know math if I try hard enough? And that’s what I did, I put all my effort into solving different math problems. And every time it was over my head and I was about to give up, I would remember you juggling and it helped me to keep trying. So, thank YOU!”