Normally I have loose wrists so if I raise a hand while playing that the hand falls down. Also the fingers are curved.
However, the pinkies which tend to get straight especially for fast runs. I need to train it that the pinkies remain curved as it is a sign of tension, so not relaxed enough. Also for fast arpeggios the other fingers tend to get straight.
My worst problem is probably that I tend to play a piece complete with lots of errors and try to reduce the errors little by little with time. So the muscle memory (and ear!) is already used to the ever appearing error. Better seems to immediately eliminate an error as soon as it appears, and not come to a stadium with a big pile of errors what needs to be cleared up. It takes sooooo long this way.
So same problem like Pianolady, I need more concentrated and disciplined practise too. In fact, I almost don't make a difference between practising and playing, it is all the time playing with occassional removal of stone old mistakes...