Packing breakfast, lunch and dinner

Thanks everyone for your awesome suggestions! I already make burritos to freeze but will definitely try some of the other ideas :)

When I wS a med student I made batches of Lime Baked Chicken (on this site and super eSy) and Stuffed Baked Potatoes (Mollie Katzen's Enchanted Broccoli Forest and still a fam favorite), froze, and carried to school. Reheated potatoes, chicken ok at room temp.

I feel your pain, I have been there. I think the most important thing is to eat as nutritiously as possible with variety and ease of transport. I suggest prepping as much food on your easier days so you can put meals together with less effort.
For breakfast I would suggest a granola full of nuts, seeds and dried fruit with yoghurt that you can transport in a jar. Or a granola bar (preferably homemade) if that doesn't work. Possibly oatmeal too (easy to prepare, travels well) but I don't find it lasts as long as granola.
Then eggs and tortillas make a great starting point for another meal. Basically you scramble eggs, add onions / green onions / beans / cheese (feta, cheddar, anything tasty) / rice / anything that isn't' wet or runny and roll or fold the tortilla. You can lightly toast /brown the tortilla in a fry pan once filled and it crisps it a bit and makes it a little tidier to eat - or you can skip this. Wrap in foil and eat when ready. You could add other vegetable but try and avoid anything with moisture, it could make the tortilla soggy.
I would have rice and baked potatoes prepared as they can be added to meals or eaten on their own - you can add beans, veggies, meat or fish. Cooked chicken works with all of the above and you can have it in wraps, salads, sandwiches. And one of my staples would be meatloaf. A slice with 2 pieces of bread is a meal, you can just eat it alone and it is filling. And of course there is soup, or ramen. However, as much as I love soup it is a tad tedious to transport when you have so many other things to carry but you can buy quite good quality packet soups that only need boiled water for any cold days or when you need that cup of warmth.

When I was in your shoes I packed a yogurt with granola and a sliced banana or dried fruit quite often. Also, baked oatmeal reheats well. Smoothies in a shaker cup are good for any meal or a snack (add some oats if you want it to be a little more hearty - eggs work too but I wouldn't unless you are going to drink it soon after making and you have a reliable source of fresh eggs).
I would often roast a big pan of veggies (squash, sweet potatoes, carrots, onions, broccoli, etc) and then pack them topped with chickpeas or black beans and hummus. You can also cook up some wheat berries or other grain and top with the roasted veggies and beans and then a tahini dressing.
Pasties are a classic "bag lunch" item. I'm not sure if they would be available in stores where you are at but they are not difficult to make - every recipe I've seen makes several dozen of them though so they take a little bit of time commitment to make them. They do freeze well though.
If you have a blender or food processor, this recipe can be mixed up in minutes (it does have to bake as well) and I've had no problems keeping individually wrapped pieces in the fridge for 2 weeks (we've never had any left after that long): https://food52.com/recipes/34869-chewy-granola-bars
I tried not to pack things with too many components that needed to be assembled prior to eating because that required more containers to bring with and more time to eat. I also normally carried around good tea bags and/or coffee in a thermos. And napkins. Bringing with a cloth napkin can make you feel like you really packed a great meal.
Also, I agree with scruz, that one of the easiest things to do is simply cook extra when you have time to actually cook a meal and then eat the leftovers for several days.

i relied a lot on pork shoulder roast, usually asian spices...honey, soy, garlic, ginger, sesame oil marinade. cook up a pot of rice. slice up the pork and lay on top rice and pack and microwave for tasty meal. sliced avocado. greek yogurt, sliced fruit, granola on top with honey parfait for breakfast. egg/meat/cheese/refried bean breakfast burrito. make pot of thick split pea or potato soup and reheat. cut up celery, olives, crackers ,cheese, sliced apples, peeled oranges, nuts. mix it up and use zip lock bags for each meal or containers that you can wash out and reuse. try not to rely on carbos but eat protein and fruit and veggies. the key is to cook extra and pack that up for meals that are freezable or at a minimum, store in fridge.

savory handpies can be filled with any number of things and don't require refrigeration usually (unless they have mayo in them (!?) on a hot day). Include in these anything wrapped in a baked pastry or dough, like filo--empanadas, turnovers, spanakopita. Trader Joe's steak burritos and filled tamales can be nuked and are tasty. Stir fries-- rice, veggies, meat- can be perfectly tasty room temp.

overnight oatmeal makes a great packed breakfast! https://food52.com/blog/9844-how-to-make-overnight-oats-without-a-recipe