Sure... I think it's a couple of things, and I hope I don't come off as being too "new-agey" but there are two things at work here, I think, which is the power of Al-Anon.
The first goes back to the whole "Power of Thought" thing. You can't hold two thoughts in your head at the same time. So by repeating simple phrases or ideas that represent "replacement thoughts" you are pushing the other, negative, angry, codependent thoughts out of your head. There are lots of Power of Thought writers out there--James Allen was one of the first and his book, As a Man Thinketh is still one of the best as far as I'm concerned.
The second is the whole "collective consciousness" thing. I really feel that energy transmitted by healthy people somehow gets transmitted into us when we're around them. That's why people say going to Al-Anon is so important. I believe that that's why people get excited all together at rock concerts, laugh more when watching a comedy in a movie theatre, even are more apt to loot when other people are doing it. If you hang around "crazy" you get "crazy." If you hang around "healthy" you get "healthy"
So keep going back for the "good vibes" of Al-Anon! It's real!