The question I'm asking today is: how do I define my purpose in life?
It may be that your true goals in life are different than the ones you set when you were 20. You're not a stupid idiot by any means, and it seems like if wanted to coast the rest of your life you're setup to do so. Be proud of getting to this point because most never will. But if you're looking for deeper fulfillment, you'll need to either set new goals or redefine the purpose for the next phase of your life.
My hypothesis is that when I resolve my purpose, I'll have stronger incentives for self-motivation.
Defining purpose is hard and it's interwoven with your world view, thoughts on religion, death, etc., but you have to start somewhere.