The mental check is important. Shooting not too many arrows is important too.
I was totally out of form, due to a dislocated collarbone and all the muscles around it. I learned myself another technique making me able to shoot anyhow.
Now my shoulder is much better and I am returning to the old and proper technique. It is amazing how difficult it is to get rid off the wrong technique! Everytime I repeat in my head, with every shot, if everything is as it should be. After three weeks the results are coming however.
I also train at different distances between the 15 and 40 yards, three arrows at the time. When I start to miss,that's for me an indication I am getting too tired and I stop.
After a few weeks 15 yards became easy,all my arows are dead-center most of the time. Just don't give up!