My definition of happiness is having enough of: health, wealth, knowledge, passion, approval, and autonomy
Your "perception" of people and events can make or break your happiness.
I think (and sorry if I'm being repetitive - I may have said this a couple of years ago on EP), my late Grandfather had it nailed when he was asked the same question. There was a slight pause, and then he said...
"Waking up on a Sunday morning, with a plate full of hot buttered crumpets, and eating them with the faint but distinctive smell of tw@t on one's fingers."
I didn't like to picture the image, but I can't fault his logic.