I believe loaded words like "subconscious" make it difficult to come up with new explanations.
It's interesting that when the body is happy and relaxed the mind is not aware of it. So there seems to be a continuous struggle between the ordering mind and instinctive body. Or the mind and the animal side.
The contentment might be like temperature in an annealing system or experimentation/forgetting tunable in an artificial system.
When we're content, nothing has to be changed, right? The trouble is, our "contentment sensor" has been evolved a long time ago for a different environment and is probably hard to train being so ancient and we do not know how to do it...
Of course this is another "just so" explanation. There's not enough science on contentment and discontent related to intellectual performance.
It's interesting that when the body is happy and relaxed the mind is not aware of it. So there seems to be a continuous struggle between the ordering mind and instinctive body. Or the mind and the animal side.