…Did I fixate at all?
Who should lift in front of a mirror and why
A mirror can be a very powerful tool, lifting in front of it can give lifters an immediate visual feedback of their form that can’t be obtained with a video, which is more accurate and can be analyzed frame by frame, but only once the training is over.
Inexperienced lifters although won’t know what to look for in their reflected image, creating a very distracting task. Also the athlete’s proprioception is not going to be stimulated as much as it would be by constant correction from a coach.
Experienced lifters will know which detail to look for, but there won’t be mirrors in front of them at their next competition, so they will do it only once in a while if necessary, e.g. if they’re changing something in their technique and want to see how it works.
Summarizing: inexperience lifters should better be costantly corrected by a coach and develop a better proprioception, veterans should use the mirror as a “treat” once in a while, but overall a video will give the possibility for a better analysis of the motion.