If you are shooting spot-on when practicing (on the ground) and then hitting high and left when hunting, make sure you are keeping good form and bending at the waist. If you are just lowering the bow arm and not keeping the upper body together, it could cause a high shot. When shooting from a treestand, come to full draw like you would on the ground. Now bend at the waist, keeping the upperbody all together.
For hitting left, do have your quiver attached with arrows when hunting, but practicing without quiver or arrows? You may be canting the bow. Just something to think about.