Too much practice

Heresy!

No less of an expert thanHarvey Penick wrote, in his little red book, "Just because two aspirin can cure a headache, don't take the whole bottle."

Just because some practice is necessary to learn the basics of the stroke, don't become a Range Rat.

First of all, every serious golfer wonders why he can't take his range swing to the course, until he learns the differences between the range swing and golf. 

1. On the range, you decide where you want to hit the ball; on the course, the target (the fairway, green, hole) is there, and you either hit it where you should or you've made a mistake. You don't get to decide.
   
2. On the range, you can hit 10 5-irons in a row, making changes until you're satisfied with the result, then hit a bunch more 5-irons, and convince yourself that your stroke is fine. But in reality, you've developed a stroke that is tailored for a particular situation that you'll never find on a golf course.

Once he gets onto a course and is playing, the range rat has in mind his perfectly tailored stroke, not the stroke he can expect on an average. That perfectly tailored stroke ALWAYS, ALWAYS sends the ball further than the expected average. Just two days ago, I stood on a par-3 hole and scoped the distance to the flag as 107 yards. The hole was cut very close to the front of the green, and the ground leading up to the green is sloped at about a 40º angle, so anything short is going to roll 20 feet down and 30 feet short. I know that, with the temperature hovering around 50º Fahrenheit and a 15-mph sidewind, my average hit with a 9-iron would be sufficient...but a sub-average hit with that club would leave a difficult, blind, uphill shot. So I took an 8-iron, and hit it pure. 40 feet past the flag, just off the putting surface. 

Even an average hit with the 8-iron would have been 10 feet past, but a sub-average hit would have a good chance of staying on the green, and would be a legitimate birdie try, given the hole location. I made my par with a simple chip and putt, missing birdie by less than a foot. And that was off of the worst possible result with the eight-iron.

What most golfers need to practice more is what I just described: analysing the situation, making decisions, and keeping score. That's golf.

Perfect swings? They don't exist.

Most serious golfers, as a round comes to a close, especially one in which they have performed more poorly than they expected (90+% of the time) will immediately head to the range to "correct" the swing "errors" that cost them their expected score. That's a waste, except for the people who profit from selling range balls. They'll never get a chance to replay today's game, and the next time they play, a different set of "errors" and "poor swings" will bedevil them again.

What the range rat doesn't ever grasp is that everyone's swing -- yours, mine, Jack's, Tiger's -- is pretty much the same day in and day out, but pretty much the same is not a pure repetition. There's so much going on in even the simplest swing action that variability is unavoidable.

Golf is nothing more than coping with that variability. You can't practice it away.