"People try to make 2 sticks and a string more complicated then it is."
How true. Never the less, I want to put as much in my favor as possible. Some things are obvious, like best possible placement, properly tuned bow and straight flying arrows, broadheads as sharp as possible, etc.
However, even with the best plains, things go wrong. I don't plan for and expect best case scenarios. Deer move as you shoot, unseen branches deflect arrows, yardage is misjudged, etc.
It has been my experience that "best case" is rarely what I experience. I like to have a bit more than necessary for best case scenarios. When it does occur exactly as planned, I am pleasantly surprised.