To make my practice session a little more interesting and informative for me, I continue my run after missing to a total score of 200, but I mark on paper the type of shot I missed. Either an A - B - or C shot. The A shot is what I mark after being completely stuck, locked up or way out of line, also a scratch. A B shot is what I mark if I miss either a long shot or a more than my comfortable cut shot, and a C shot is a no brainer that my wife could make (who never plays pool)
This helps me understand my concentration level. I miss more C shots than B shots and lastly A shots. Bottom line is I end up beating myself. This has helped me with what I call understanding my "mini zone". I know, call it crazy but thats what I call it. My mini zone is the feeling I need to reach on each shot before I pull the trigger. If I don't accomplish this feeling of concentration and confidence and clear picture of the outcome, I know I'm setting myself up for a miss. I'm now much more aware that this is one of my primary reasons for missing.