If your having problems with your break sometimes going back to the basics helps.
I had some problems with my break for the past two weeks and ended up going back to the basics and it help.
When i practice my break, I start out breaking soft, to control the CB, and then slightly increase my power untill i cant control the CB anymore, and thats when i know how hard i can break and still control the CB.
if you PM blackjack, he had some very good info on mastering the break. I dont know if he still has his web site up but it has the best info you can read about learning to control the CB. and it really does work.
And yes reading too much and thinking too much can hurt you more than you know.
I know some people say you should stand and hold the cue when your breaking just like you would if your shooting a shot.
When I get into my stance for breaking, I rarely check for my hand position on the cue. I just feel for when i am holding the cue confortably, and get into a strong stance for breaking. Its kinda hard to explain, so if someone at your local pool hall gives lessons, they can generally help alot better.