I'm a student too so I know what you're talking about.
The thing is, we really need to plan out our week. We already have a rough idea of how our week will look like.

I know its not always the best thing, but frozen vegetables really aren't that bad, especially if you don't have time to run in the store every couple of days.
I always have an organic pasta sauce ready for those quick meals.
Whenever I make a salad dressing I make A LOT. I prefer honey in salad dressings because honey is antibacterial and I keep it in the fridge for a couple of days.
Low carb?I respect your choice but personally I can't do that. My body absolutely needs carbs, especially in school. If I don't get enough of them I'll eat anything that's not up on tress at the count of three.
Our body sends us hunger signals when it need carbs actually, which is why we usually eat sweets or bad carbs when we crave food.
When your body got everything it needed in a meal it usually doesn't react to the dessert your friends eating.

Hope it helped a lil bit