Unfortunately, many kids enter into my office (I'm a therapist) without any idea how to talk about their feelings. When I ask them a question about how they felt about something, I sometimes get a deer-in-the-headlights sort of look. They just don't have the language to verbalize how they feel.
Kids who can't talk about their feelings are much more likely to show their feelings. And it isn't likely to be pretty. An angry kid who can't say "I'm mad" is likely to throw a fit. A kid who can't say, "I'm frustrated," may hit his brother.
Kids can't learn how to deal with their feelings until they have the language to express themselves. Once they have the words, they have a chance of expressing how they feel in a more socially appropriate manner.
Many parents don't ever talk to kids about how to deal with their feelings. As a result, kids sometimes think they are entitled to feel happy all the time. When they're bored they want an adult to fix it. When they're mad they expect their parents to solve the issue.
It's important for parents to take note their job isn't to raise a happy kid. Kids don't need to be satisfied all the time. In fact, working hard to make sure a kid never feels uncomfortable feelings is going to do more harm than good. Kids need to learn how to tolerate feeling sad, angry, scared, and disappointed.
Learn how to teach your child about feelings and you'll likely see less behavioral issues. You'll also be providing your child with a life-long skill that will help him into adulthood.