What is the secret to understanding emotion?

For my whole life I have attempted to best define the words people use when they're expressing some heightened mental state or experience that evokes memories and body-impulse reactions. I know they are called emotions and I have studied the Anthropological, Sociological and Psychological reasonings for human emotion but no book tells me what they are. I don't know what happy is other that the antithesis of sad which is just a word with a definition, synonyms and societal parameters. WHAT DOES SADNESS FEEL LIKE??? HOW CAN I TEACH THOSE IN MY LIFE TO BE MORE PRECISE AND DESCRIPTIVE TO MAKE UP FOR MY DEFICIENCY?