What truly intrigues you?
What are your unrealized talents, and which of those would you like to use?
What is your personal mission and what impact do you want to make in this world?
I think these are all good starting places for anyone determining their initial career path, or having a change of heart / midlife introspection. It still amazes me that many people I encounter go through the career motion almost aimlessly, only finding this area of their life continuously underwhelming and having cascading impacts into other more important areas of their life. Life's short, don't settle for mediocracy.