Good form involves not only body alignment and reference but also involves pacing of your steps. When you're learning something new, no matter what it is, it's good to start slow. Another good technique is to break it down into small steps.
Sounds like you can come to anchor okay. I would recommend, before even starting your draw, decide that you're not going to shoot that arrow. Draw your arrow, come to anchor, hold for several seconds, then let down. Do this for the next several practices to train yourself to have full control of your release.
I would then recommend coming to anchor, deliberately holding for several seconds (3 or 4 seconds), then releasing the arrow. Again, you want to teach yourself that you have full control.
Mix this up, go between letting down and shooting. Or have someone else call out whether to shoot or let down when you're at anchor. As it becomes ingrained, you can speed up your shot as needed.