Happens top us all.
And I will say a clean miss is WAY, WAY better than a poor hit.
Shakes your confidence up. So what you have to do is go out and shoot some stumps. I think we get into a pattern where we practice at one distance so the eye and muscle reflex are geared for that. Then a close shot comes and we just pull and release without PICKING A SPOT. I know that is what my post blooper analysis revealed. I was walking back from my stand mid-day a few years ago and a large doe was walking down the same path. I stopped and, at CLOSER than 10 yards, I put an arrow right over her back. D'oh!
So go out in the woods and practice some 5 yard, 10 yard, 15 yard shots.
When I first started bowhunting (still-hunting) I had many, many opportunities that I never capitalized on because I was afraid to draw. Waiting for that perfect moment that never came. I'm not sure if it was buck fever, fear of being made, or just over-awed by being that close to a deer. This is not to say being reckless is called for - but the fact you got a shot off at a close deer is a good sign.
I've also watched deer drop and bolt and it is astonishing how fast they convert energy to motion and dropping to get the legs bent for a push may take them below your arrow.
Wait until the deer appears relaxed and then get the arrow off. Here's hoping you next opportiunity comes soon.