I'm not positive, but I think what AA means by powerless is if you will pick up a drink in a sober state KNOWING where it takes you, then you've lost power in that area. Also once you have one drink and you can't stop, then you've lost power.
I've never read "take what you need and leave the rest" in the Big Book. With my crazy thinking I can't trust what I think I need or don't need.