I think it affects a lot of us. Almost analogous to driving on the road with our full concentration through a hazardous patch vs. allowing us the luxury of "distractions/comfort" for our brain when we're purely relying on muscle memory in normal driving conditions.
Somebody posted a wonderful thread earlier on about "Confirmation" vs "Falsification" as a starting point for their thought processes. If I were allowed to paraphrase, it basically said that good chess players start every position out as a state of crisis and even when they isolate a candidate move, they become fantastic pessimists, constantly in a state of "mental anguish" as to why that move will FAIL. This will continue until they prove that they can no longer figure out why that move is bad ....and then play it!
This is in contrast to the vast majority of us who tend to be relaxed/happy with most positions and then find a move to "keep" us in this relaxed state. In other words, we tend to look for moves that "confirm" our unguarded optimism in the position.
The former "state of mind" seems to be the way to go for stronger play. The actual article can be found here:
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.117.8670&rep=rep1&type=pdf

In the course of the Chicago Open I was working on one problem, making weakening moves, that can be described as a logical problem. However I also noticed a psychological problem. Whenever a plan went well, when I ended up a little better, or turned a losing position into a draw, I would relax. Almost immediately after that I would make a blunder. The blunder would really be a form of regression where I went back a stage or two in my development. While the logical problems require awareness and a few times of reapting the mistakes, the psychological problem might require a different approach. Because, when something good happens at the chess board there is naturally relief and a decrease in tension and stress. Unfortunately these good feelings, while very pleasant, make me a worse player. I think what I need to do whenever I feel good, is to get up and then refocus treating the new position as the beginning and trying to get back to the sense of urgency I had at the beginning of the game.
Is this something affecting others as well?