Some activities lend themselves to flow. Immediate feedback, commensurate challenges and skills, and clear goals are all precursors to flow. Lack of these makes flow difficult to achieve. Some people are inclined to flow. They set goals even when apparently doing nothing, and are able to focus their attention easily.
Flow tends to result in personal growth.
By engaging in flow, your skills develop, requiring greater challenges to maintain the balance needed for flow. I always was convinced, for some reason, that it was more or less all right to do whatever you liked, as long as you truly loved doing it. Perhaps it's coming of age in the 90's, but I've never had the impression I would have only one career. I have known for years that computer programming was a flow activity for me, and working on these pages is also turning out to be a considerable source of flow. You can be happy without a million things.