I must respectfully disagree with the comments about mental issues and confidence. IMO, playing well happens because many small physical things happen to sync up -- some of them seemingly insignificant. The mental state is just a manifestation of confidence felt (and perhaps mild euphoria). Many of us here are often focused in on one or two of these things, like a grip, or bridge, or stance. Sometimes we're able to see them as part of a process.
I think playing well or even "dead stroke" visits us when we're doing one, two, or maybe more things differently than before. Some of the changes may be so small, we deem them unimportant and they go unnoticed. Perhaps a bit more of a step to the left, establishing contact between bridge hand and cue shaft with different motion, a slightly longer or shorter bridge, a longer or shorter grip, a slightly turned wrist there, a higher or lower head, a more level cue, a longer back stroke, a more relaxed or tighter bridge, and so on. On occasion, all this comes together to produce a precise stroke and the ability to do what we will with the cue ball. *Then* the mental part comes to us and we become absorbed by our ability to execute shots with sharpened precision. The next day, we go to the table and, because we're not machines, we do it all a bit differently.
Way back when, I would notice that if I just played very quickly, without thinking, I could play "very well." I would run around the table, collapse into a stance, throw a hodge podge of sometimes unorthodox bridges on the table, and zip the balls into the pockets. I could run a lot of balls this way. The problem was that this "system" wasn't reliable enough to count on. Nowadays, it's more the opposite. I find that it's when I'm concentrating on the balls and table, considering every nuance of the upcoming shot, position play, table layout, and using a very studied technique, that I play "very well."
So why the difference? I think it’s because the words "play very well" have a different meaning for me now than before. The lack of reliability that I experienced as a younger player was because I just wasn't good enough. The failure of my "system" was my failure as a player. I could only play so well and missed the balls and position plays I was suppose to miss -- at the time -- not knowing I was suppose to miss them and instead blaming my "system." Now, I think I have a better appreciation for how difficult the game can be, and can more clearly see what I don't know and might not be able to execute. I also now know, with much more accuracy, what playing "very well" means. Many times in the past, I thought I was playing "very well." Now, I have a much more narrow definition of those words and they require a much higher level of precision and consistency in execution than I would have used even just six months ago.
So what does this mean? I dunno. Perhaps it's just that playing well means different things to different people and different things at different times in our lives. Certainly, "dead stroke" for a player that has only been playing for a year or two, means something quite different to a player with twenty or thirty years of playing experience. And because we keep "raising the bar," dead stroke always remains elusive and a very hard place
to get to (think carrot on a stick).
I guess I’m trying to say that playing well = playing your best for the level of experience, knowledge and talent you've amassed up to this point in your life and that that level is a moving target as you accumulate more practice time, match play, and knowledge.
Lou Figueroa