Having recently spent time on crutches, I found it's a little harder to home school when the teacher can't carry anything! Seriously though, it got me thinking about who would school our child and how, if we were seriously incapacitated (God forbid). We do plan for a lot of possible scenarios, but this wasn't one of them. I know a few home schooling moms this has happened to (flesh-eating bacteria, cancer) and it has forced us to start formulating a plan (maybe even detail the plan in your will, along with custody).
As for the difficult days, I naively expected there wouldn't be any because I'd make everything so fun! RONTFL! Twice a week we have a treat jar for best effort work in Handwriting and Math. If attitudes need to be adjusted those days, the first treat is lost...that usually takes care of it. On other days, I've given my child time-out in an empty hallway, doing nothing silently for 10 minutes-usually takes care of it. I try to figure out first though, is my child acting up because we've been over the material once before and she's gotten it and she's bored or just a general whinyness (getting tired/hungry), or just plain challenging authority. If it's tired/hungry, we'll take a break. Whiny or challenging gets an attitude adjustment. If it's boredom I may present it a little differently or I may have her work through it anyway because I want her to learn sometimes you may have to do something again (like on the job).
As for my attitude, sometimes I need an attitude adjustment too. I may scrap my lesson plan and we do something else (like find & indentify bugs outside, talk about & practice measuring while we bake, make snack and practice fractions, look for hidden words inside of bigger words, pack a picnic and visit an art show or gallery locally, play a spelling game while we're driving to the grocery store (she asks for words to spell). If we're ahead, I may declare a vacation day and we play together, I may sew clothes while she reads (sometimes to me)/watches a Magic School Bus or Schoolhouse Rock video/draws/plays, or we may read lots of books together. We may practice skip counting money when we play Life or talk about artists while we play playdough. I've found for us, sometimes we need to step away for a day or two, refresh, and jump back in. Home schooling is like anything else, sometimes everyone just gets tired of having a routine.