Do you think you can have only one job in your lifetime? This is not true, but lots of people think so. For example, when people decide what to learn in college, they think the decisions they make now will decide their future jobs. However, here are many examples in which people achieved (实现) their dreams after changing their jobs later in life.
Ronald Reagan was an actor when he was young. Later, he decided to do political (政治的) work. The love for it made him become President of the United States.
The famous artist in the 19 century, Vincent Van Gogh, was not a painter at the beginning. He once was a preacher (牧师). It was only 10 years before he died that he decided to become an artist.
J. K. Rowling, the writer of Harry Potter, was a school teacher before she began writing books. Actually, she was out of her job before the first book Harry Potter came out.
Now we know jobs can be changeable. The important thing is to find what you are really good at or what you really want to do. Once you find what you love, try your best to do it.