Your son lives in the now because that is all he can do. It's not a preference. If everybody were to live in the now, we wouldn't even have agriculture. Of course it's good to relax, but this line of thinking seems pernicious. It's great that adults are constantly harried by life's demands.
Agreed, with conditions. It is still possible to live in the moment and still have all of the tools that the higher brain functions give you, i.e. planning, forecasting.
The key is to plan in the present, then do the next thing and the next thing, each time in the present. Living like this requires adult versions of faith, agility and resourcefulness.
Even with planning, there can still be time for: "when you are hungry, eat. When you are tired, sleep". Not everything needs to be planned. Big things do, but not everything does. Know when to deploy the higher functions and when not to.
