Here's an episode of Seth Godin's Akimbo podcast that has been banging around my head since I heard it a few weeks ago: Ignore Sunk Costs.
The basic idea—although you should listen to the whole thing—is that the time and effort you've spent in the past working on something or becoming something is like a gift from your past self. And you don't have to accept the gift. You can say "no, thank you".
I suppose that's a natural concern for a middle-age human with basic needs taken care of. Am I on the right path? Who knows, anyway, right? Keep on straight ahead, or head left or right at the next fork. It's how I feel about my two diplomas in aerospace engineering. (I haven't seen those in a while... I wonder if they're still in the closet...) It's how I feel about the arc of my career so far. It's how I feel about some organizations and relationships and investments and clothes and habits and so on which just hang on in some niche of my life, and it's not clear always if they're serving me or the other way around.
But thinking about these things as a gift from a past self that I can refuse helps to relieve the pressure. No, thank you; or, still, yes. It can be a new decision. It doesn't have to be an old decision that got locked in forever.
Here's another version to listen to by David McRaney on You Are Not So Smart: The Sunk Cost Fallacy.