Happiness comes from solving problems. The keyword here is "solving." If you're avoiding your problems or feel like you don't have any problems, then you're going to make yourself miserable. If you feel like you have problems that you can't solve, you will likewise make yourself miserable. The secret sauce is in the solving of the problems, not in not having problems in the first place.
To be happy we need something to solve. Happiness is therefore a form of action; it's an activity, not something that is passively bestowed upon you, not something that you magically discover in a top-ten article on the Huffington Post or from any specific guru or teacher. It doesn't magically appear when you finally make enough money to add on that extra room to the house. You don't find it waiting for you in a place, an idea, a job—or even a book, for that matter.
Happiness is a constant work-in-progress, because solving problems is a constant work-in-progress—the solutions to today's problems will lay the foundations for tomorrow's problems, and so on. True happiness occurs only when you find the problems you enjoy having and enjoy solving.