Hi, Fraido! Congrats on finishing high school
It definitely sounds like you are off to a good start by drinking only water and cutting out any junk food. It is amazing what a difference it makes to simply not have it around. A lot of what helps is meal planning and grocery lists...eliminates a lot of the temptation.
For healthy breakfasts, OATMEAL. Cheap, filling and you can always change up what nuts/raisins/fresh fruit you add to it. If you have a decent blender, green smoothies are nice too (but can get a bit expensive).
I also agree with the other posters that eating more plant based (and this is coming from a girl who loves to eat meat) can do wonders. Even just cutting your meat portion in half and doubling your accompanying veggie. A good sized sweet potato simply roasted can be almost a light lunch on its own. And veggies like Brussels sprouts, broccoli, cauliflower, asparagus are all super easy to prepare roasted with just some salt and pepper.
Soups are a really good way to go, too. Find a good recipe, make a big batch and have it for breakfast, lunch or dinner throughout the week.
Sorry if that was a bit disjointed but those are all things that have worked for me
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