When I first switched over to traditional bows many years ago I had a good friend that helped me quite a bit. This guy was/is both an accomplished 3D shooter and hunter. Anyway, I just couldn't quite pull it all together, so my friend suggested we do some night practice. He stuck a shiny foil gum wrapper on my bale and the only light was from my kitchen widow some 50 yards from my practice bale. We did a "walk back". Shoot an arrow, walk back a few steps, then repeat, paying no real attention to distance. Normally shooting 3 arrows, all from different distances and my friend would just tell me to "stop, concentrate on the the shine, shoot."
I was amazed at the size of my groups...no lefts or rights and after a few rounds, the highs and lows were more than acceptable. Still today, 30+ years later if I am having any shooting issues I'll do a little night shooting and thing tend to tighten up nicely.
I think the lack out outside distractions allows you to focus on nothing but the little "shiny spot". I modified the "night shooting" later on by wrapping one of my son's soccer balls with duct tape and then putting some small squares of reflective tape on the ball. Then I would kick it around the yard and shoot it with judo points. A piece of relective tape on the arrows is a good idea to help locate them in the dark. The duct tape wrap will definitely make the soccer ball last a little longer with the judos or you can use rubber blunts.
I bring this up because I've been experiencing some shooting woes here lately. Just came in from a night shooting session and it's the best I've shot for awhile! Give night shooting a try. Not only is it a lot of fun it may improve your shooting!
Mike