How to find what I am really good at?

In the past years I’ve been quite diluted in my personal and professional life. Changed several jobs, and in my hobbies, I am jumping from one project to another. How do you stay focused? How do you find 1 thing you are really good at and stick with it? Is there a book or a blog teaching this? Although, it seems quite trivial, for me this is a huge live hurdle.