This question was asked of me when I was interviewing for the job I now have (I must have given a good answer). It wasn't just "what are you good at?" but what gets you up in the morning and excited to get to work?
Think about when you were a child, what did you like to do? Did you like sports? Heading out to the woods on your bike? Boy/Girl scouts?
Back when I was in the Navy, I had a supervisor tell me to figure out what I liked to do and bring that to whatever job I was working at. In the field I was in, you would typically have a new assignment every year or so. I figured out early on I liked to help solve operational problems through technology. This involved understanding the big picture and how to improve operations, something I continue to do to this day.
Another way to think about it, if you were writing a novel about yourself, what would your story be? If you can envision that, why not make it a reality.