Happiness is a state of exaltation, inspiration, in which a person who follows his or her vocation, destiny, is. He follows the path of his dharma
The Explanatory Dictionary gives a partial interpretation of the concept of happiness, but the Ukrainian Wikipedia expands on the topic quite well.
According to Aristotle, happiness is an action in accordance with one’s nature. Fish are happy to swim and birds are happy to fly. Instead, human nature is characterised by the ability to think and create political organisations, so the happiest people are philosophers and statesmen. However, Aristotle did not underestimate the role of physiological needs (he felt that a happy person should be well fed).
Wikipedia
The Vedic definition of happiness summarises most philosophical interpretations and makes it possible to apply this concept in practice.