I think time and practice will help. He's never experienced this before and it doesn't feel nice. Do you model this stuff for him and emotion coach him? Make a mistake, point it out and talk about your emotions? Like "Oh MAN! I messed up that bank transfer! Oh DRAT! That is so frustrating! I paid the gas bill twice and forgot the electric bill. Grrr, I'm annoyed at myself because now I'll have to remember next month to pay less on the gas. Oh well, I'll just go an do the electric now. I suppose it's nott hat big a deal, but wow do I feel annoyed, maybe I'll take a walk, etc". Show him that the emotions are OK, and normal, and show him how you deal with them. Help him with perspective, too.