pellmell This is a really late response to this comment, but I was just lured back onto this thread by recent posts.
I agree that proper mechanics can be achieved and that they do heighten your chances of playing better golf. Like I say, I think you should always be working on your game and trying to improve it (if the game is at all important to you). But I don't think you should be in perpetual "rejig mode," particularly when you are on the course.
I play with guys (my dad is particularly bad) who never seem to just stand over the ball, look at their target, and make the swing. They're constantly "working on things": "Ya know, I just don't think I'm getting over to my left side quite right, so I'm going to...." Then that won't work, or it will work for a couple of shots (or games) and then not work, so they're off "working on" something else. (I have place working on in quotations because they're not really working on anything -- they're just reacting to single events.) And they'll change what they're working on about two or three times through the game. They never get to the point where they say (as Steve said beautifully), "Well, this is the swing I have today, how am I going to claw and scratch my way to a decent score with it?"
In my mind, by the time you get to the point where you working on your swing while on the course, your game is basically over for the day.