I have one child in particular that tends to be a perfectionist. My other child is just in math - not sure what happened there.

I remind my dc that if they got everything right all of the time, why would I need to teach them? There are going to be new things they are learning, and they are going to make mistakes. I also tell them that if they got everything perfectly right, I would probably want to move them up a grade so they began missing things, for they should not know everything they are learning already. I've also told them that about 1/3 of the skills in a guide are usually skills they have already learned and should have pretty much mastered. 1/3 of the skills they have had before, but the year will be spent learning more and strengthening those skills. 1/3 of the skills are totally new and are meant to be in the practicing mode. So, 2/3 of the skills are not meant to be things that are mastered. I have talked about how God lets us miss things, mess things up, and make some big mistakes to remind us to be humble, and to help us to have compassion for others. I gave the example that I used to be very upset if someone was late, but then I realized I am late sometimes too. Unless I can be perfectly on time all of the time, I cannot expect others to be, and even if I could be "perfect" in this regard, do I really want to be so hung up on that? It's exhausting trying to be perfect, and it's something we will fail at every time. It helps my ds for me to just to have the "big talk" about this once and a great while, but most times, if he makes a mistake, it's best to show it to him very matter-of-factly, tell him to quickly fix it, and remind him we are wasting time by talking about it. If tears come, I hug him and tell him I think he's doing great in school. If this doesn't work, I have him go to another room to collect himself, and then I do something else until he's ready to be calm. I have prayed with him too. Okay, I just asked my dc what I've said that helps them get past mistakes they've made, and they said the most helpful things I've said are...
"Put on some happy music and pick a better attitude."
Or,
"No surprise you made a mistake. Everybody does. Me included. Just get on with it."
Or,
"It's normal to miss things like that. Your brother does too."
Or,
"Buck up, or you can head to time out."
Yeah, I probably have said that last one a few times before.

I just want to encourage you that this is pretty common. Wow, I thought all the deep talks we had were so helpful - but I guess they find the one-liners more helpful.

I hope something here helps, but I guess the best advice I can give is not to let the child dwell on it by devoting lots of time to it. HTH!
In Christ,
Julie