It is said that his mother often considered him a nuisance and treated him harshly. Joseph was purported to be slow to learn and absent-minded. He was said to frequently wander aimlessly, with his mouth gaping open. And, he had a bad temper, so, he was not at all popular. He tried to learn the trade of shoemaking, but failed. He asked to become a Franciscan, but they initially would not accept him. Finally he did join the Capuchins. However, for a very short period of time. Eight months later, they sent him away. Sources say it was because he could not seem to do anything right.
He dropped piles of dishes and kept forgetting to do what he was told. His mother was not at all pleased to have the eighteen-year-old Joseph back home again, so she finally got him accepted as a servant at the Franciscan monastery. He was given the friars habit and put to hard work taking care of the horses.
About this time, Joseph began to change. He grew in humility and gentleness, fruits of the Holy Spirit at work in a person. He became more careful and successful at his work. He also began to pray more do more voluntary acts of penance. Finally, he was able to enter the Franciscan order and, eventually, study for the priesthood. Although he was a good and holy friar, he had a very hard time with studies. During his seminary exams, the examiner happened to ask him to explain the only thing he knew well, and so he was ordained a deacon, and later a priest.
Learn more on St. Joseph of Cupertino: http://www.catholic.org/saints/saint.php?saint_id=72