Two year old slaps and scratches himself and we can't stop him.

My 28 month old seems like most other 2 years old we know but one thing that he does that concerns us is that when he gets frustrated he will start to slap and scratch himself, and he does it hard. He actually used to hit us or other people before and we made it very clear that was unacceptable and now he virtually never does that. However he continues to hit himself and even when we try to tell him not to he just repeatedly says "sorry mommy/daddy" but continues to hit himself almost like he can't help it. The trigger for it is generally also something small (e.g. he's trying to set up his blocks in some way and one of the blocks falls over).Of note, my wife also had issues with this for a few years, but as an adult. Basically it was kind of like a nervous breakdown behavior but through counseling and therapy she stopped doing it. I don't know if that's all related but I mention it for context.In any case, my wife and I don't know what approach to take with our son. Of course we want him to stop, but it also seems inappropriate to try to discipline him for his behavior because it seems like he can't help it and that he's consciously hitting himself because he realizes it would be wrong to hurt someone else (so in some ways, it's almost a considerate action on his part). We've tried to talk to him calmly, both during the actual incidents and afterwards about healthier ways to deal with his frustration but it either doesn't help or he doesn't quite understand us.Has anyone had similar behavior to this or have any other insights? via /r/Parenting http://ift.tt/2lhXFz7