My daughter (second-grader) has a 10 word spelling test every Friday at school. We found that we were battling her each week because she didn't want to study, so we came up with a plan. If she gets 8 out of the 10 words right then she can watch some TV over the weekend, if not, then she can't watch any TV until she can spell all 10 words. This has been really effective. Since we started this plan she's gotten at least 8 right every week and the fights over studying have stopped. Until yesterday, when she only got 7 right.
She was pretty upset about it. And I was heartbroken to hear her reaction. She's always been a kid who likes to be right and she takes it particularly hard when she makes mistakes. In this case, she spent a while crying and when I tried to reassure her she went full-on self doubt. When I told her all she needed to do was look over the words for a while and we'd give it a shot she said, "But I can't do it! I do everything wrong." Of course, those words break any parent's heart and they fill me with dread. I don't want my daughter to feel that way about herself or her abilities and I don't want her to be frozen by self doubt when difficulties arise. In the end, we had a good talk about all the things that she does right and we talked about how helpful it is to check the stories we tell ourselves. When we tell ourselves that we can't do it, we won't; but, if we tell ourselves that we can if we try, we will often succeed.
Some kids learn this lesson easily and others need more support and reminders. My wife and I have been working with our daughter on this and she's a little less hard on herself than she used to be, but it's a long process and a difficult balance: teaching a child to push themselves to do their best, but not judge themselves too harshly when things are challenging.
In the meantime, we're making an effort to be proactive when it comes to letting her know when she's done well. This is as simple as remembering to verbalize it when we notice that she's done something right or given a task her best effort. But we're tempering that by maintaining our expectations of her - 7/10 on the spelling test is still not enough. The way I see it, maintaining high expectations is a way of showing respect. Kids aren't dumb. They know when they're doing their best and when they're not. If my daughter's teacher asks her to learn 10 spelling words and she only learns a few, it's kind of insulting if I tell her she did well. It's like saying, "We didn't think you could do any better than that anyway." However, if I only pay attention when she falls short, she'll develop the idea that she's no good and that my expectations are impossibly high for someone so flawed.