I agree with the Grinder, stand taller. Also, visualize a target in line with the pocket and just a few inches from the OB, and focus on sending the ball through that target- once you visualize that line, just put the pocket out of your mind completely. Finally, don't forget about throw on these shots. Using a paper aiming aid is a good way to develop a sense for the amount of throw at different cut angles, with different spin, and varying stroke speed.
Aim Circle from Easy Pool Tutor
The attached file is an improved version I made (I believe the original idea comes from a Babe Cranfield book). Let me know if it doesn't print with the right dimensions, and I can post a vector image.
EDIT: OK, so how do I attach this image so it will just appear as a filename you can click on instead of displaying the actual image in the post as big as a poster.
EDIT: I went ahead and removed the image until I figure out a better way to attach it. That thing was just way too big.