One other thing I forgot to mention is make sure you have a solid sight picture that allows you to see the back and front of the arrow.
I've had problems missing left (still do get the occasional miss left, more than I'd like).
Sometime's it's as simple as the front of the arrow appearing as though it's pointing straight but in actuality the rear of the arrow is pointing to the left causing left misses.
This is where heavily canting the bow comes into play as it puts the line (the whole arrow) directly under the eye so you can see the front, back, and middle of the arrow and keep it lined up on target.