Flow is a state where attention is focussed on a task that is at the right challenge level. Not too easy to be boring, not too difficult to be discouraging.
The amount of time that a person spends in flow is directly linked to the amount of enjoyment that they get out of life.
And when I say “task”, this does not mean that it has to be work-related. It could be speaking to a friend or family member, writing a diary entry, playing a team sport, etc.
Getting the difficulty level right is important, and the issue is that this is a moving target. Between discipline and skillsets, a person is likely to improve at different speeds, but they will generally improve with repetition. This is why we can easily get bored doing the same thing again and again because the initial challenge is lost.
Being able to make things more complex in a creative way is important.
I enjoy walking, and I found that by layering my passion for photography into my walking, I pay significantly more attention to my surroundings and get a more enjoyable walk. What would have been a routine walk in my own thoughts, I now start to notice small details about where I am that I had not previously noticed.
Same person, but a different level of attention.