Hmm, this may be turning into a book blog... Stay tuned, I'll be posting less fluffy stuff as well.
It is a familiar phrase - "do what you love", and it has been repeated over and over again at several hacker/security cons all over the world. I do not know about you, but it took me some time to sit down and figure out what I love. Being a book nerd, I picked up Business Model You for some inspiration. It is a strange book, somewhat an offshoot of a very successful (apparently) book Business Model Generation and applies the same framework to individuals instead of businesses.
What I really liked about this book is not the "business model". Instead, have a look at Chapter 4 "Who are you?" It has a lot of great advice on figuring out what it is that you really love, if you do not know it yet (many people do not).
A thought experiment. Think back to any time before you were 20 years old:They include a bunch of other thinking prompts - e.g. thinking over what events in your life related to what feelings, what kind of environment you like to be in and so on, yet this "inner teenager" exercise is the most unusual and most powerful. Obviously these memories need to be re-interpreted in the world you are living in, abstracted, re-applied - the core idea still stays.
What did you love to do? (I do not think the authors include sex under this rubric, hehe)
What activities - games, hobbies, sports, extracurricular events, school subjects did you enjoy? Recall your natural, uncoerced proclivities.
Think about what kept you absorbed for hours and made you happily oblivious to the rest of the world. What tasks made time fly?
So, people who love what they do are following their inner teenager..
P.S. If you are wondering, I love solving complex puzzle-like problems (preferably computer-related), working alone or in a small group of peers who share goals and learn from each other. The rest is, erm, syntactic sugar.