Poor instruction can have repercussions ...
SAC Bloggs undergoing trade training was subjected to continued verbal 'encouragement' from a particularly abrasive Cpl. Nevertheless Bloggs passed the course and went to his new Unit.
Time passed, he did well, so well that he applied for and gained a commission.
He eventually arrived at a Unit as JEngO where, lo and behold, the abrasive Cpl (now a Sgt) was being his usual self. Our JEngO had the Sgt marched in to his office (with hat!).
"Well Sgt, we meet again. You do realise that your career stops here. Dismiss."