The quote in the previous post captures the essence of flow.
Striving for happiness as an end in itself is flawed logic .... flow delivers happiness as a by-product and is like something in our periferal vision that disappears when we focus on it.
To achieve flow is the trick .... and that can be though any activity.
I remember my short time as a waiter at a friend's restaurant. At the end of the night I felt absolutely exhausted but it was such a great feeling of accomplishment ..... doing a good job (mostly), interacting with folk, working with friends, earning some extra money ..... a good days work, as they say.