I didn't realize how ingrained it had become until a particular stage in a USPSA match. During a mag change I failed to fully seat the fresh mag into the Glock 22 I was using at the time. The round in the chamber fired followed by a click when the next round failed to feed. I looked down to basically watch my hands do a tap and rack and continued shooting. The RO complimented me on a nice recovery although I'm not proud of failing to properly seat the mag in the first place.
I agree that repetition is the key. It isn't always necessary to go to the range. A lot can be practiced at home with empty mags/speedloaders and dummy rounds.