Is it interesting or boring? Correct the mistakes, please! Thanks a lot.

When I was a child and studied at school, I didn't like history. I thought it was very boring thing. I thought, how can it be an interesting subject if these events took place many years ago?! Some events happened thousands of years ago. In what way is it important to us, modern people? I thought, ancient people had boring and hard lives. I pitied those people. Once, some years later, I read a book which was written by a Soviet journalist. It was not a modern book, and I found the book by pure accident. He visited a lot of countries, and wrote about their history. In turns out, that people have always had interesting lives. Sometimes, they cried and sometimes they laughed. Now it is the same way! Wonderful events have happened. I like to read historical books now.

Can you find the joke in the following sentence?:

When I was younger, I wanted to be a historian, but I changed my mind when I realized there was no future in it.