Okay, so I buy some canned stuff (tomatoes, chickpeas) to have to add to meals when I need to bulk up things, and I always have lentils, rice and beans in the house. I usually make sure I at least have a plan for what I'm gonna eat for a few days - when I have the mental energy I go to the fridge and plan meals. The fact I know what I'll eat tomorrow for at least one meal makes it way easier. A checklist helps - every meal needs a source of protein and a source of carbs (not an exact science but this fits with what I usually like eating) and I add veggies and seeds to everything.
I usually prep half of the meal in advance - example, I'll buy chicken and cook it, then divide it in three boxes and store it in the fridge and have one with a bag of frozen veggies, one with rice, and one with another thing. You can do this with vegetarian meals too. You can heat stuff up in your oven very easily (I tend to not care about this that much I eat cold food all the time, but that's me). If I have leftovers, I either eat them for breakfast/dinner, or I combine two leftovers. I usually prep up to four meals, and make a little more than I need to, so I can have that in the fridge. Bulk cooking stew/chilly/beans, dividing into a few parts and adding other stuff to it for variety daily. I tend to like my veggies raw-ish so I don't cook them a long time.
Another tip is having a list of meals you can do when you literally can't even. I feel like grilled cheese (toasties?) would be on your list. Frittatas with mushrooms and peppers is on mine. Basically, something you can do even when you can't do anything and that will make you feel full and better, with stuff you always have at home. It helps you save money on takeout, and it is generally healthier than it. Though sometimes you will have takeout and that is fine.
Hope this helps!