Matt, I totally agree. I just started using back tension and set my wrist release to do the same after a bout with a handheld I didn't care for. I set my wrist release pretty touchy and started using my back to pull through the shot. Its a hairy feeling at first when the bugger goes off unexpectedly!![:-] But ya know what? Most times the arrow was right where I was aiming. Of course the other times...well....lets not go there.
I had target panic too and still do occasionally. Most times its a matter of letting the bow lay for a day or two for me. The above suggestions are great. If you live on or near a farm where you can get a big round bail to shoot at, shoot at it for a couple days with your eye's closed. Just focus on pulling through the shot nice and smooth.
I don't neccesarily think a complete suprise release is required to shoot at your best though. Getting a smooth consistant release is what I think is best, especially for hunting where you may need to command a shot. Its much easier to do this consistantly using your back muscles than it is with you index finger.