As long as hormones in your body that are produced naturally are occurring in the correct amounts, then all of those hormones are responsible for happiness. However, there are certain hormones that take credit for leading to happiness. This hormone is called endorphins and endorphins are commonly known as the happy hormones because they make you happy.
Your body produces these hormones on a consistent basis, but there are ways to make these hormones produce more to make you happier. One key way is to exercise. Now, after a very grueling workout, you may feel extremely tired and therefore not feeling the happiness inside of you. However, a walk every day will secrete these endorphins while not making totally wiped out. You will soon feel the happiness after your walk.