Yes it may have been, its really good for when you tense up over the ball as you can't be jabby, you have to be smooth it also stops you worrying about technique to much
Most of the coaches seem to be of the opinion that you should firstly only worry about the speed needed to get to the cup. If you are pin high regularly then you can factor in break etc afterwards, but, at least you should not be 4 foot past the cup. I am sure that I read that tour pro's only make 47% of putts from 6foot. Aim to hit no more than 18" past and when you can do that regularly then worry about holing it, using the correct line!
It still sounds as if you decelerate into the ball and stab it which is going to be inconsistant in judging pace. If you add the variance of breaking wrists at all and I don't think it is necessarily a mental issue. I still advocate a single putting lesson. Get him to check your alignment and make sure everything is parallel to the target line, particularly the shoulders and let him see where you are gripping the club. It really will be value for money.