Maggie Mason, when speaking on finding your passion, suggested that you ask, "What do I do when I'm sick and I have no energy to do anything and can't sleep?"
Look for the thing you'll do even when you're tired.
See where that intersects with the skills on your resume. Notice topics you keep going back to, even as other aspects of your life and career change.
It's this "core of who you are" stuff for which you want to be making space.