I actually train two methods of 'high stress aiming'. The first is front sight only aiming. At short range, putting just your front sight on the target and practicing so your draw almost more or less always levels the pistol. This way you can reliably hit your target center mass at short (self defense) ranges.
The second method (and one I'm really becoming a fan of) is a method taught to me by some of my marine buddies. I'm not sure of what to call it. Basically, with a two hand grip, the thumb of the dominate hand raises up to make a V with the barrel. You put your target between your thumb and your barrel and you should hit center mass. Repetition allows your groups to be tight.
Neither of these methods are accurate in the sense that you can shoot right between the eyes or hit the exact spot you are aiming at. The advantage here is it gives you a general point of aim without a lot of effort. This works really well for me with guns like the LCP which have rear sights I really can't use.
I still practice target shooting (I have a really nice ruger 22) and standard shooting fundamentals weekly, but when I'm shooting my carry, I'm working on speed to target and center of mass accuracy (rather than target shooting accuracy).
I also sometimes practice "zen shooting". This is where I shoot my target without aiming or trying to hit it. I point down range, relax, think about a spot on the target and when the moment strikes, I shoot my gun. This is similar to kyudo's seisha seichū (correct shooting is correct hitting). Basically, I focus on connecting myself to my target and pushing the bullet to the target. It's relaxing and I tend to be more accurate when I go back to normal shooting at the end. I also tend to always hit my target somewhere with this method.