I used to hunt years ago when it wasnt as popular as it is now. I found out that when i shoot from the stand there isnt a difference in shot placement. some say to aim lower, etc. I never did and had several perfect hits.
This question comes up a lot and the best advice anyone can and will give you is:
Practice shooting from your treestand at the same height as you would while hunting, in your hunting gear. this way you will build up confidence in your abilities, shot placements, yardage estimations, etc.
by doing these things you will also find you will have less of a "Buck Fever" hit you. I am a firm believer that buck fever hits those people harder that know deep down they arent prepared or that havent practiced a lot.