I like to step back and look at the big picture. I find something positive about whatever the child does when working in the difficult area. I love to remind my children that I'm more proud of the fact they try when they face a challenge than when they succeed at something that comes easily.
Sometimes, I will find something that really matters to that child. If it's an object, I will buy it. If it's an activity, I'll make it a flashy certificate. I tell the child that when they reach a defined goal, it's theirs. I keep it in sight. The goal might be just making a reasonable and consistent effort. I make it clear it is totally up to the child. And I provide whatever support is needed.