One thing that is common to any happy life is the consistent experience of the state of flow: a state whereby the world dissolves to nothing but the task at hand, each step so challenging yet clearly reachable, beckoning you to strive onward.
For those who experience flow often, I salute you. To those that don't, experience it first-hand now! Whether It be the seamless coordination of cooking a great meal, or the enthralment of playing your favourite video game, everybody needs some flow on a daily basis.
From those activities you can draw knowledge of what makes you tick. Unsurprisingly, the way that you conduct your daily life will determine how you develop your own, idiosyncratic, definition of the ideal flow state.
As an example, here's how I approach programming. I'll always start by thinking about, but not doing the hardest problem of the day. This is usually an architectural decision, one which affects everything built atop it.
I'll think about it for 5 minutes, then tackle some trivial tasks (like re-arranging code to make it flow more logically and look pretty) while I let the idea bounce around in my head.
10 minutes later, I'll try to solve the hard problem again. If it fails, I'll get back to easy problems. If I run out of easy problems, I call it a day.
So that's my definition of flow in programming. And of course, it doesn't happen all the time. Which is why I have multiple hobbies which their own definition of flow.
For example, making these scribbles is a matter of sitting down for an hour with some good music. Whereas writing these words was done in complete silence and in multiple short burts.
The great thing is, whatever my mood, I have a practical model of flow. =)
So here's an ode to flow: a reminder that happiness is a constant flow