GREAT question.
And MOST DEFINITELY the RIGHT question for ANY archer at ANY level to ask.
But, as TnDeerGuy wrote:
This actually is somewhat of a complex question.
And I agree with his assessment.
I also suggest that as you spend time in the deer woods, you will begin to understand the body language of the deer you hunt. And exactly where you aim with a bow has a lot to do with how relaxed or alert a deer is prior to the arrow release.
For example, it is not unusual for a doe to be standing at fifteen or twenty yards stomping her foot. BUT...is she stomping her foot 1-while periodically looking back over her shoulder, or 2-is she flaring her nostrils while stomping and flinching and dropping her chest toward the ground, ears laid back, and eyes WIDE open?
While number 1 may mean there is a buck approaching her from the rear and she is agitated but NOT spooked, number two may mean she has got a good whiff of YOU, and is about to "explode" away.
While a shot at number two may be IFFY at best, the first shot might just mean to aim a little lower.
A good bet is to always figure out, for a BROADSIDE shot, with or without a slight quarter, where you need to aim to hit the heart. WITHOUT hitting the shoulder bones like the humerus, or scapula. This way, if the deer drops a little, you'll catch both lungs. If no drop, you will likely hit heart AND probably lungs.
But the easy shots are just that, EASY (or at least "easy ER").
It is the difficult angles that will cause you to have bad dreams. The shot angles that are NOT that common for practice, that are NOT familiar.
Steep angles, longer than usual, odd quarter too or away.
Tight shots, walking shots, RUNNING shots, or otherwise POOR shot selection shots. It is the PRESSURE shots that make you think, "well, I HAD a shot, I just did not take it because I was either un-familiar with the shot, or did not know exactly where to put my arrow to kill it effectively".
This is one aspect of archery we CAN all practice. And there are some GREAT videos that help teach it. It takes a little effort, but is WELL worth it when you aren't talking about the ONE shot you had, but did not make. Instead, you are standing over a dead deer SHOWING your buddies at camp where you put the arrow.
Study deer anatomy VERY WELL. Learn exactly where to put that arrow at ANY angle and ANY body language so that it affects a quick, clean, killing shot.
And MOST importantly, learn when to PASS on a shot that will most likely NOT work out for you, or the deer.