Throwing out food constantly is killing my grocery budget

I'm trying to be smart about groceries but I keep wasting food and watching money go straight in the trash. I meal plan, check what I have before shopping, all that stuff but things still go bad. Produce rots way faster than I expect. I buy ingredients for one recipe and the rest sits until it spoils. Every time I toss something it just feels like I'm burning cash but I don't know what I'm doing wrong. My freezer is tiny so I can't just freeze everything and my schedule is too packed to meal prep on weekends.

How do you actually use everything you buy without stuff going bad? I need to figure this out because my grocery budget can't handle all this waste.