Life around here is a little unpredictable. What is appropriate for dinner sometimes depends on whether the baby is being quietly happy and cooperative, or fussy and difficult, or I am exhausted because she has been fussy and refusing to nap all day. It doesn't really work right now for me to plan out specific meals on specific days. I also don't have time I want to spend of writing a new meal plan every week. On the other hand, having no plan means it gets to be dinner time and everyone is hungry and I have nothing quick and simple to fix. That in turn results in grumpiness.
My current approach is to have about ten standard meals and keep the ingredients for them on hand all the time. When I run out of something, or it gets low enough that I can't make that recipe again, I write it on my grocery list, which is stuck to my refrigerator with a magnet along with a pencil. I periodically change some of the recipes in this list to keep things from getting boring.
This solution works pretty well for me. When dinnertime rolls around I just go to my list and pick something appropriate for today's situation.