When you study pro rallies, and see when they miss, it's always due to: late coil turn, or wrong contact point defense. No one misses when they coil early, unless it's a no pace jamming ball, and they miss due to their bodies slowing down, or hitting too far out in front on no pace shots.
They miss high volleys, or high groundies, when they hit late, and they go long. Sometimes they hit too early, and go into net on high shots, but it's far more often a late contact. Talk to Roddick about that high bh volley that cost him a wimby. Too late, and missed wide/long.
It's almost impossible to be on the right spot on every shot in a match. But if you know why you are missing, trying to maintain the same contact distance, on every shot, and not coiling early enough, you can be more aggressive in fixing those errors during a match.