Here's a trick I learned: if you want to learn to do something really well, find something that's even harder and teach yourself to do that instead. Then when you come back to that first thing, you'll rule at it...as if by magic.
The music I make involves isolating different parts of your body - your hands and fingers are not moving together. Adding vocals into that can be like asking someone to rub their belly and pat their heads on a pogo stick. And then there's my new favorite thing - drumming on the soundbox while I'm singing and/or playing with the other hand (probably the least period thing I do, I'll admit, but hell it's fun). You have to be able to isolate parts of your body in order for them to do their thing independently.
So rather than just practice this over and over again until I got really good at it, I've decided to learn to play the drums! My husband's a drummer and is teaching me on his drum kit in the basement. We've started really simple, but it's still a bit of a mind-trip. I'll have my rhythm going, and then my mind will wander for a second and suddenly my foot and right hand have switched places...or have synched up...or my left hand goes "Whut???" and starts flailing randomly.
The really interesting thing is, I have to really clear my mind in order to get into a groove. Now, I've always found this to be true with harp as well - as soon as I start thinking about how my day was, or this section coming up that I always mess up, or how amazingly I'm rocking this section I always mess up on...I mess up. My mind has to be blank, filled with nothing but music and sensation in my fingers, in order to do really well. The same is true with the drums, only it's WAY harder! You get into a groove, it gets repetitive, your mind starts to wander and BAM - suddenly you're playing unison quarter notes in each limb, which is not what you were going for. You basically have to meditate in order to play well. No wonder my husband does it for stress relief (and here I thought bangin' real hard on stuff was enough).
Anyway, it's fun and I think in the long run learning to play the drums will make me a better harper. I love it when life works like that!