There will be some situations where you need to substitute an ingredient, or something in your plan.
If you can’t have gluten you will be alerted to substitute these items in your plan. Thank goodness the choices for gluten free products at most supermarkets has increased enormously in the last few years. Even if you don’t suffer from a gastrointestinal condition like Coeliac disease, you may find bread or pasta makes you feel bloated, sluggish or heavy. We steer away from these things as it tends to be easier on the digestive system.
If there’s a particular spice or herb you don’t like, no drama. Just use the same quantity and swap it for one you do like. Some people like their food spicy, some don’t. If you’re not a fan of chilli you can leave it out.
If you want to fill out a meal more, you can add green vegetables. Go crazy with the green beans, broccoli, spinach....again they have great nutritional value and really low calorie counts.
Sometimes you’ll go to the butcher or supermarket and they won’t have the meat you want. That’s ok too. Just choose something similar. If it’s meant to be turkey and you can’t get it, go with chicken. Meant to be lamb - but that’s a no go?... beef will be fine. Common sense will usually tell you what to do.
If for some reason you need to switch the days around in your week, or an evening meal gets swapped with another evening meal occasionally, it’s ok! This will not derail your whole week.
Maybe one day you get to work and realise you forgot your prepared lunch. Just make the best choice you can, opting for minimally processed foods and get back on track as soon as you can. There is no point stressing about it.