For me a successful meal plan factors in that it's hard to predict exactly how the week pans out. I'm a big fan of having ingredients ready prepped in the fridge so I can assemble meals quickly. I'm vegan, so for me that means I have one or two types of pulses ready cooked in the fridge (they keep for around five days either in water or dressed), vegetables ready sliced or diced (root veg in airtight containers in water, other veg just sliced or chopped in airtight containers), some veg is great steamed and ready to go (sweet potatoes, butternut squash).I also gave one or two grains that takes longer than 10 minutes to cook (brown rice, quinoa, etc) ready in the fridge. I typically prep on sundays, but I'm not religious about it.
I then have several meals in mind for the week, depending on exactly what I've got in.
For example, I can make a quick lentil loaf (sautee onion, garlic and carrots with rosemary, add cooked lentils, oats, some stock and mustard, mix, put in loaf ton, bake) and put some veggies on a roasting tray alongside it.
Next day I might have stir fry of my ready prepped veg with rice noodles and a satay sauce.
The following day veggie burgers made out of the quinoa, some steamed sweet potatoes and beans. Served with a salad and potato wedges.
And then perhaps a veggie chilli with some brown rice.
But there are lots of meals you could create from those ingredients and that's the point. Maybe it gets hot and you just want a big salad with beans,steamed veggies and a nice dressing. Or you want a hearty soup. You can go either way, which means you aren't ridgedly stuck to a meal that no one fancies at that moment.
Home cooking is about being flexible within a structure. I'd hate to start each evening completely new. But I also dont want to eateftovers all the time. Prepping ingredients is a good compromise.
