I haven't found the same issues with you as shooting at tennis balls. Of course, that's not all I shoot at either. I typically shoot for about an hour every day at a variety of targets. Leaves, stumps, clumps of grass, dirt clods, plastic bottles, spots on dirt banks, etc. I never think about the distances. I usually only take one arrow, too.
My bag target has a worn out hole in the center that is about the size of a deer's vitals area. I don't have a problem picking out a spot within that to hit, even though it's essentially all brown. On my block target, when I did shoot at it, I shot at the solid white side.
When shooting at game, I've never had the slighest problem in picking a spot to hit. Now, I certainly haven't hit my spot every time, but that's a different discussion.
I might add that I don't take a lot of really long shots at live game, either. Well, maybe a rabbit or a field rat, but never at big game. I usually am shooting at a "see the hairs" distance.