We usually do several things at once. We drive a car, talking on the phone. During negotiations with the client, we receive emails and surf on the web.
Intensive mental effort can cause distraction, then you should:
• focus on a single task,
• every now and then (after reaching the next stage) take a break to ventilate the mind, with intense mental effort, take several minutes a few times within an hour: look into the distance or close your eyes and ... think "about nothing",
• after long sitting work, get up from time to time, straighten your back, stretch your limbs,
• try to close one task before you take another one.
I hope that these short tips will help you relax even during the greatest mental effort.
Remember that rest is needed for each of us.
Have a nice day ☼ @quilath