John always wanted to be a dentist and was very determined to become one. He would always try to flatter his teachers by telling them he wanted to be a dentist. However, in the back of their mind they never believed him. One day when John woke up, there was a blizzard, so school was canceled, he was so happy. John continued studying dentistry up until 15 years later, when he turned 22, he finally became one and proved everyone wrong.
Hope it works! :)