Flingblade,
You have to ask yourself what it was that making you let go early. You may have been having the "Good Enough" thought coming from the gremlin. It sounds like you got ahold of the issue though. I seems that you are directing your thoughts into the proper areas.
There is no reason that you can't shoot the way you are describing, however, you need to make a choice to only shoot the shot if it is perfect in concentration. If you are letting go of bad arrows and failing to let down, you are strengthening the gremlin. You need to become more in tune with your thoughts. If your frame of mind is not right during the shot, LET DOWN!!!! I know that is a tough choice to make during a shot, but it will work as a defining moment for you. There has to be defining moments in your archery. A shot that was really tough to concentrate on because of outside stress, maybe you had to let down twice, but once you do that, you will really be in tune with your thoughts. Furthermore, you will be able to repeat it, time and again. Good luck!!! Call if you can.