... and not proving the rifle set up before you need to use it. Personally, I would say that accounts for probably 50% of the missed out there for long range hunting, ...
I'm pretty careful about this yet this has caused me two flubs in the past 4 years. Both times the rifle was bumped enough to move the POI. I like to shoot the rifle just prior to entering the field to confirm POI. In spite of this I still got bit in the butt. Can't do enough to protect the rifle/scope setup from bumps and jars after the last confirmation shooting.