use this as a part of your learning curve , none of us is perfect we all have a great deal different experiences,
chances are good the deer may recover if it was a flesh wound,
you can,t change the past but you can learn from mistakes and improve going forward!
look if you were learning to ice skate and fell on your butt!, its just part of the learning process, and youll improve if you concentrate on the basics and learn how you initially may have screwed up, in this case Its probably related to rushing the shot and crap shot placement... your certainly not the first nor will you be the last to make a less than ideal shot.