It’s easiest to not eat junk by just not buying junk to begin with. I noticed I stopped eating TV dinners as often when I started taking them off my grocery list. That forces me to think about what I want to make. Might be as simple as whole wheat pasta for dinner with a smoothie (unflavored yogurt, milk, frozen berries, a banana, and spinach).
While I’ve certainly done it myself, I’ve noticed my SO tends to go to town on certain snacks like chips or Ritz over regular meals. This has helped me also realize that it would be beneficial to myself to also cut down on the amount of snacks foods I have. Going too far in the other direction (just having raw ingredients only) also incetivizes eating out though, so a balance must be struck.