I have found life so much easier since I started meal planning about 18mths ago. Before that I was a sahm and shopping, cooking, baking etc were fun and sort of a hobby / interest for me. We all loved that phase 
Then I went back to work and coupled with living in the country not close to any shops and dd in school and activities fitting in spontaneous shopping needs became a real chore for me. As did thinking to myself in work 'we have chicken in the fridge, I will make such and such tonight' only to get home to discover we did not have 1 vital ingredient. It all became a bit stressful. I also like to ensure that we have variety in what we eat and that dd (can be v fussy) eats well with plenty of veg as often as I can rather than quick freezer dinner options like pizza etc.
I plan by looking at what is in the freezer / fridge and larder and then have a think about what we haven't had in a while. It's still the same old rotation of ingredients but I try to vary it up a bit so mince can be bolognaise, cottage pie, chilli, burgers, lasagne etc Same with chicken and fish etc.
I then write a list of dinners I would like to have by mentally using the things in stock already and adding what we don't have to the list.
Then I shop. I always leave lee-way for bargains I might find in the shops and we have a good sized freezer so the first thing I do when I get home is stick 90% of the meat / fish into it to keep it as fresh as possible. This keeps meal plans flexible as the expensive stuff is not going off. I plan 7 - 10 meals but which nights we eat them on depends on lots of things such as activites, last minute plans, not feeling like a particular thing on a certain night.
I try as much as possible to incorporate at least 2 times in the week where there are in-built leftovers for the next night, i.e. this week we had beef & red wine stew on Sunday and again yesterday. Tomorrow we will have roast chicken and chicken satay on Thursday etc. That makes life a lot easier.
I have been 'dinner' planning a long time but in recent weeks as I do this I also write down lunch ideas and lunchbox stuff to make sure we have enough for the week. This has also made life a LOT easier as I know there is always stuff in the house to feed us all.
I love dashing out of work these days knowing I don't have to make a pit-stop at aldi, racing against the clock, before school pick up and knowing that the fridge is full and we can eat well that day. It gives me a great sense of well being for some reason.