When I was 10 and just learning how to hunt, I was walking in my dad's woods (about 8 acres with farm land all around and a major highway on the back end) when I came across a partially decayed dead deer. He was an 8pt with an arrow still sticking through his ribcage. The smell made my stomach turn but not as much as seeing that big beautiful buck wasted when my dad had taken the only deer he saw all season, a button buck.

My dad came out with me to see it after he got done with work and he guesstimated it has been dead for a week or so, and bow season had ended a week earlier.
He was pretty sure it was my neighbor's arrow and took it to him to see if it was.
When my dad told him where he found it, he shrugged and said "Well, ya can't find 'em all."
We went back and walked it off, the deer was 200 yards from where his stand and you could see the stand from where the deer was. My dad made me swear then and there that when I was old enough to hunt on my own that I would never waste a deer by not tracking it.

In 20+ years of hunting, my dad has only lost 1 deer. It took 9 hours of looking in daylight, 4 more by flashlight and 7 more hours the next day with our dog before he finally gave up with tears in his eyes. I know a lot of not losing a deer is luck, but there is a significant amount that depends on desire to find the deer and the amount of effort you're willing to put into finding it. I've been fortunate in that my 3 deer have ran a combined total of about 200 yards before dropping, I just hope that when the time comes, as I'm sure it will sooner or later, that I have the same discipline as my dad to find my deer or at least not give up on it without a monumental effort!