I plan my meals Monday through Friday ahead of time. That way I know what grocery shopping to do and I don't have to THINK about it during the week. Stressing about food makes me crazy right now, and I just can't put effort into thinking about every meal as it comes up.
Sunday night, I plug my meals for the week into my calorie counter. Then, as the week goes on, I modify and adjust as necessary. Oops, didn't have time for breakfast on Tuesday? Delete it. Oops, went out to eat on Thursday? Delete what I'd planned and add the restaurant meal. Etc. Etc. Etc.
I also menu planned WAAAY before I started calorie counting, so the change wasn't a huge adjustment for me, but on weekends, I just track as I eat (or at the end of the day). Even obsessive planners like me need freedom sometimes.