Cook food that will freeze, so what you usually make becomes batch cooking. This works for ragout, chilli, curries, casseroles, chicken traybakes.
Go for simple food - an omlette and salad; a single portion of pasta with mashed avocado, sliced sundried tomatoes and garlic fried in the tomato oil, with a sprinkle of chilli flakes and squeeze of lemon.
Cook things you can make different the next day. Eg roast or poach two salmon fillets. Have one on day 1 with steamed rice and broccoli, have the second in a stir fry with soy, spring onions, edamame, choi and noodles, or with pasta, peas and herby low fat cream cheese as a sauce. Or cook two chicken breasts. Day 1, in a wholemeal wrap with salad, smoky paprika stirred into mayo or yoghurt to make a dressing, day 2 with pesto gnocchi or tossedin a pan with yoghurt and curry spices, served with rice.
If you know you can't always be bothered, buy some ready cooked pouches of smoky beans in tomato sauce, or lentils or steamed rice etc. They taste freshly cooked but have a longish shelf life. Better than just having a sandwich every day. Or get a couple of healthy ready meals - lower fat curries (Waitrose are very good); ready made falafel with a nice humous, salad and pita.