I have noticed a lot of people dont set there stand height appropriate to the distance of the shot.
Some guys always hunt high, or always hunt low rather than thinking about where they are best concealed, have the proper air current, and most of all, where they will perform the best shot placement.
The higher you are in the tree, and the closer you are to the deer, the more severe of an angle, and the more likely to achieve a dreaded "one lung hit"....