How do you all think of what to cook everyday?

I buy groceries once a week, counting out the days. I try to buy variety. And each evening, I plan what to make the next day. The decision might be, " we have a lot of leftovers, so I'll heat them up again tomorrow." Or it might be, " I'll defrost something that is very different from what we have been having lately." (Perhaps fish). Or it might be, "I'll heat up the leftovers from two nights ago." Or, "I'm tired of meat. Tomorrow night will be potatoes and eggs with fried eggplant." Or, "I'm going to be busy tomorrow evening, so I will put something in the crock pot in the morning."