I think the best way to ensure you eat healthily is to plan. You need to have an idea of what you are going to cook for the week, as well as what to buy at the supermarket. Below is an example of a weekly shop and meal planner. I find its the best way to stop overeating and also to ensure you eat a balanced diet, with the right kind of snacks. OK I am not always regimented and of course have my off days, or treats. Also if you are not that into cooking or short of time, then it is best to plan when you are going to cook bulk meals, so that you ensure you eat properly throughout the week and do not get lazy by wednesday!
Shopping List example for one week: Mushrooms, Zucchini, Green Beans, Baby corn, Capsicum, Lettuce, Tomatoes, Spring Onions, Sweet Potato, Avocado, Lemon, Kiwi, Pomegranate
Vegan sausages, Chickpeas, Lentils, Rice Noodles, Quinoa, Frozen Berries, GF Granola
Fish, Lactose free Yoghurt, Lactose Free cheese, Lactose Free Milk, Eggs

Meals from this weeks shop: Lasagne with Lentil Ragu, Quinoa Salad with Fish, Veg Stir Fry, Fish with rice noodles, Chickpea and Vegan Sausage Casserole
Lunches: Egg Salad, Salad with Fish, Sausage Sandwich, Quinoa Salad
So to start to plan my shopping list, I think of a couple of lunch meals and a couple of dinner meals and ensure I have enough items to make breakfast as well.
For example, I plan to have berries with granola for breakfast every other day, with a smoothie on the other days. For lunch, soup for three days of the week, with salad every other day, this makes it easier to plan what to buy and when to cook. Of course you can cook every day, like me, but I know some do not like to do that.
Dinner a casserole (two meals), fish dish and Lasagne (two meals), this will equate to 5 meals. Remember that generally a meal will keep up to 3 days in the fridge, or of course you can freeze most items.
I try to group foods together to ensure it is easy to shop. I know some ingredients if you have never used before are sometimes hard to find in supermarkets, like chipotle chillies or truffle paste. But look in world foods or just ask, or pick it up when you see them.
Obviously it takes time to build up your different store or fridge items, but just pick one up a week and before you know it, you will be eating different and interesting flavors. Be adventurous!