I have read many times that the brain uses about 20 per cent of the body’s energy for processing and transmitting information through electrical signals. Much like the CPU of a computer the brain uses a disproportionately higher amount of energy than other parts as it is busy coordinating this complex orchestra.

Can we control the systems of the body with it’s trillions of daily events? Nope, no way, too complex. There must be an “intelligence” at work here beyond the thinking mind.
Does “over-thinking” or a racing, compulsive mind use MORE energy? Check your experience!
Hard physical work can be physically tiring yet leave our state of mind fresh and invigorated. This is accompanied by a sense of accomplishment, a healthy appetite and a restful sleep.
Hard mental work is very similar as long as it is not personal… creating art, building useful systems, solving a challenging problem at work or helping (serving) someone in need brings the same sense of accomplishment and does not leave us exhausted in the same “drained” way. During these activities the sense of a “person” or a “doer” is not present. Effectively we lose ourselves in the activity.
A very damaging combination is performing an activity while resisting that activity. Whether it is physical (eg. shoveling snow) or mental (eg. doing your taxes), the resistance to that activity will tax the brain. Not only do we have to complete the work but we must keep up the parallel task of resisting – exhausting!
Eckhart Tolle has said that resistance to “what is” is madness. Accepting what is here can oftentimes be challenging but is always an opportunity to reduce/transcend our tendency toward mental complaining AND helps to reduce/eliminate “brain drain.”
Non-duality invites us in every moment to recognize that invoking the thinking mind is not necessary. Complete focus on a task, physical or mental, leaves no room for resistance or unnecessary mental commentary – freedom!
“When sitting, sit. When walking, walk. Above all, don’t wobble.” – Mark Richardson
“Chop wood, carry water.” – Zen saying