If misery, ennui and depression are at one end of the spectrum of human happiness then flow is at the other.
Flow is focus and engagement, mind and body coordination, self actualisation call it what you will. When time passes and we don’t notice. We are “on it”, “in the zone”.
Whether it’s baking a cake, building a wall or tending sheep the task in hand is a wholehearted one, not necessarily an easy one but engrossing and ultimately satisfying.
It’s not grudging or overthought. It’s job satisfaction; non alienated work.
We all recognise it, it’s easy on the mind, we know it’s good and we feel productive.
There’s more on the science of flow here and a good reading list on the website.