It is not as difficult as you think. I go shopping twice a week, buy lots of vegetables, salad leaves, herbs, onions, garlic, plus some fruit,; chicken, salmon and/or tuna, plus eggs; Greek yoghurt, cottage cheese. Periodically get lentils, chickpeas, brown rice, whole-wheat pasta.
I batch cook. Panfry a large piece of salmon or vegetables. Oven roast chicken pieces or vegetables. Enough for at least 2 meals plus spare to add to salads. I also boil quantities of lentils or chickpeas at a time. Takes very little time.
Currently I have cooked salmon, chicken, lentils, vegetables and salad mix in the fridge. I also make a week's worth of salad dressing at a time. With these ingredients I can assemble several meals in 10 minutes or so. Maybe cook some rice, pasta or lentils if I feel I need carbs.
Minimal willpower required because I don’t feel hungry. Protein really satiates you in a way sugar, carbs and UPF don’t. I treat myself every now and again. I feel so much better about myself - and wouldn’t want to mess this up.