I believe that some poker players try to concentrate too hard in the course of a poker game. They burn themselves out in the first hour and can’t play extended sessions in top form, even when the games are very profitable.
Uncomfortable
Concentration is good in poker, but don’t force it to the extent that you’re uncomfortable. That may only add pennies to your immediate profit, but can actually cost you money overall, because you don’t pace yourself. By focusing just on what’s important — increasing observation when you’re competing in a hand — it’s likely that you can get more hours into profitable games.
Doing it that way, you’ll still observe as much as possible around you whenever you can. But you’re allowing your mind to relax when needed and recharge between hands that you play. You’ll mentally relax sometimes, but not always — just when your brain is rebelling.
More good hours
If you can get 10 hours of play with a winning expectation while being kind to your mind, that’s usually better than two hours of intense focus that are slightly more profitable. — MC