next time when you begin to draw back on your deer close your eyes and go by feel,,, once you feel your anchor is solid then open your eyes and pick the spot,,, this whole process takes a second but if you shot low at 15yds you short drew the bow or dropped your hand to see the arrow fly who knows..
as far as the miss itself, its no biggie if it was a clean miss you just laugh about it and store it in that part of your brain where you remember it forever,,,,,,, the bad misses AKA the wounds they really hurt and take more thought.