Wow this brings back such awful memories of my older 3 and I dread this stage with my younger two, it sounds like you have tried to handle this well enough. One thing I did with my kids when they were so self defeating was to minimize my reaction. I did not overly praise something simple they did like a plain colored drawing....or a basic thing they made so that when I did offer lavish praise it was because something they had made had gone above and beyond...I also did not allow self destructive bahavior and tried to curb their over reaction as well. I have a rule they could not destroy their work...this makes for too much work for us all afterwards and they always regretted it too. Draw the line there and explain if he is not satisfied then he can practice more later but sometimes as parents we must say "done is right" and force them to move on, striving for constant perfection is sometimes not helpful or healthy..that being said my nearly 16 yr dd has enrolled in college now probably because of her intelligence and her drive for perfection BUT we carefully monitor her potential for being overly perfect, she has to still remember she is a teen and their brains are still growing, there is more to learn. I say explain to your son that learning is a marathon and as adults we are still learning...this is not a sprint, no need to rush and try to master it all now...if he wants to set aside the work he is not happy with and once the rest of his work is through say he still wants to change it or re-do it then fine, but not in the heat of the moment, not in or out of anger. He needs to learn that frustration and anxiety can be something we all must learn to deal with and we cannot always do better, especially when upset...stand back and watch if he chooses 30 minutes later to still re-do the work and if he does and has the time and ability to do so without it making him nutty then allow him to improve himself and his work, under the right circumstances.
good luck
E.
