Aim small miss small......Aim big miss big

Hello, I have been a compound shooter for the past eight years, and have recently started shooting traditional(long bow). I am totally hooked on this type of archery. My question has to do with grouping. I practice out of a tree stand that I have set up in my backyard. Lately I have been using squares of toilet paper that I just drop any where in the yard. MY problem is not with the small target, actually I do very well and get just about all of my shoots with in 5 to 6 inches, if not on target. The problem comes when I move to a larger bag target that has vitals of deer on it. I really try to focus on just on spot, but it seems my shooting isnt as tight as with the smaller target. Is this something that I can get over? Any help or advice would be greatly appreciated.