An article I read by Mike Caro said it best. I can't find the article, so I'll paraphrase.
Basically, you need to know your style. Whether it be profitable or not, you have to establish your style to the point where you can get back to it. Then, you make changes to your play... just a tweak here or there. If your game gets better as a result, great. If not, you have to know how to get back to where you were. Too many players have a profitable game, make one or two changes, then become losing players.
Caro compared it to a buoy in the ocean, I think. Unless you can get back to your winning ways, you might drift endlessly, overcompensating and trying to change too much, until your game doesn't resemble your old style in any respect.
So, I'd say create the foundation of your playing style. Play a lot, so that you can easily fall back to this style whenever necessary. This is where experience is so important. Then, when you make changes or add "moves" to your repertoire do it carefully. Don't shift several points of your game at once, because you won't be able to tell which one had the most affect (positive or negative) on your game.
For example, "Joe" is a standard nit. He only plays the top ten hands, but plays them strongly. He's doing ok, but he relies on better than average cards to do well in a tournament, and his results could be way better. Instead of shifting to a full-on loose-aggressive style overnight, Joe starts raising unopened pots in position with less-than-premium hands. (small pocket pairs, high suited connectors) Then, once he has played a lot of poker, and is sure that this has improved his game (and his ROI has increased), he starts to 3-bet light against certain players in certain situations; something the old Joe would never have done. But, if at any point his game deteriorates, Joe has to dial back to his last winning style, and examine why the change didn't work.
The thing is, people do this unconsciously. It's a fundamental part of learning something new. But, sometimes just being aware of what you're changing, and why you're changing it, can make the transition from "good player" to "better player" that much easier.
Now I'm sure someone will post the real article, which will make much more sense than this.