What does it mean to be "thriving"?

I was reminded of a certain word today... And a certain goal: thriving. What does it mean to thrive? How can one tell if one is thriving? How can one help oneself thrive? Am I thriving?

I don't feel like I know the answers to any of these questions, entirely... With the possible exception of the last one... Which... Well, let's just say that today didn't feel very "thrive-ish", if you'll allow me the coinage.