Without mental and physical challenge, humans become enervated and depressed. But a surplus of either can lead to similar symptoms. Maintaining a cycle of various kinds of activity and rest will help to keep your body and mind working efficiently.
STRESS
When our muscles and bones are stressed beyond their usual capacity, minor damage occurs at a cellular level.
When we are mentally stressed, whether emotionally, or by being forced to learn something new, our brain responds to the stimuli, processing and storing the new data, and adjusting our metabolism.
RECOVERY
After muscles have been stressed, changes are made that cause them to become stronger, with a larger supply of blood. Bones respond in a similar way, increasing calcium concentration and blood supplies to the stressed regions.
No-one seems to have any idea of how rest, and in particular sleep, works. But we do know that people who get plenty of it cope better with stress than those who don't.
And repeat...
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