I' ve been bowhunting for 12 years and shot plenty of deer already, and I still rush my shots on occasion as well. I think the key is just running through a set scenario in your mind before and during the shot. Every time you practice go over the mechanical steps of the shot. Draw > Look through peep > Pick a spot > hold the pin steady > breathe > shoot. After you do that enough times it becomes habit and hopefully you' ll be able to do it when the time comes.

I shot about 1" over the back of a nice 8 pt on Saturday morning for some reason I haven' t quite figured out yet. I wasn' t nervous, I held my pin dead on him, breathed, relaxed, squeezed my release, and over the arrow went. Sometimes it just happens I guess.