I'm in a current confidence slump as well right now. This is my 9th year of archery hunting. In that time I have only killed 7 deer with my bow, 5 bucks and 2 does. So I honestly don't have a ton of past successes to fall back on. Over the last 3 seasons is where my issue lies.
2012 I shot a doe at 40 yards out of a high tree stand. I shot left pretty badly and hit her front shoulder. Fortunately I had a steep enough angle on the shot, it hit vitals and she went down about 30 yards away. Same season I had a great opportunity on a nice buck. Was hunting from the ground, stopped him broadside at 30 yards. I again shot left and hit him in the shoulder. No downward angle, he lived.
2013 I only had one opportunity at a shooter buck and shot under him. It was a longer shot (45 yards I believe) but I am (was) more than confident at that distance. I'm pretty sure I hit my coat sleeve on that one though. Either way it still doesn't help the confidence.
Finally, last year I hunted pretty hard through November and late in the month I finally decided to tag out on a doe. Again hunting from the ground, she was about 20 yards away and I shot left, really bad. Hit in front of her shoulder but broke her neck or something, she went down on the spot and I put another arrow in her. Not sure exactly why I'm shooting left on these deer but I am. Thinking I may be forgetting to follow through in the heat of the moment and pulling my bow. Either way, its one of those things that I just need to get through.