Why is irritation (internal state) removed by physical activity?

Any normal physiology is pleasant. Including, of course, sex, but not only, it is food, and digestion, and breathing, and sneezing, and movement. The movement is very physiological, almost all organs and systems are involved in the movement, and therefore pleasant sensations cover the whole body, relieve stress and irritation.

First, fatigue. The brain no longer has the strength to replay the same events and start over.

Secondly, when we, for example, run, the body thinks that we are "running away from the tiger", i.e. we are in danger. Therefore, endorphins, which were mentioned above, are splashed into the bloodstream in order to cope with the pain shock if the tiger suddenly catches up with us and bites off a leg.

These endorphins cause a feeling of "pleasant fatigue" after sports, which "dampens" irritation .

Movement stimulates the production of endorphins - the so-called hormones of joy. Runners, for example, are known for the "runner's euphoria": people in general often get stuck on sports and mobility primarily not because of health benefits, but because of the pleasure they bring. By the way, when stressed, it is best to move - to walk or even run, wave your hands, etc., it will immediately feel better.

I can assume that irritation initially builds up in the absence of the level of physical activity you need. And then - oh, miracle! - it is also removed by it. This is the simplest explanation based on the data you provided; there may be others (about some kind of hormones and all that). Thanks for a simple good question.