"Happiness is an effect of doing what you love, not an end goal to be achieved"
I've had this quote in my head for several years now and it really resonates with me. I think about this a lot... how there is no "destination" to reach in terms of happiness and self-fulfillment. You may think to yourself once 'I have that job then I'll be happy'. After that it may be 'once I get that promotion', then that fades and your happiness will be dependent on something else like that dream vacation, or once you find someone to love, and so on.....
Overall happiness, for me is that feeling of being content and looking around on any given day and smiling because life is beautiful.