Continuing the theme of self-awareness/sensitivity to improve technique let us look at the use of a witness.
A witness is good for safety, reassurance and feedback.
Over time reassurance is less important as the paddler becomes more confident, safety is a personal thing.
Unless the paddler is calm and using the minimum required effort then they will not develop self-awareness and sensitivity to be able to take comments on board and change their technique or in time become self-aware.
A lot of paddlers listen to the comments but then apply the same amount force, take the same line or use the same strokes this makes the witness of little use. #WorkInProgress