I had to work on this issue. I used to massively overcook. My house was always the place people just showed up. I had two kids, friends, family, so I was constantly ready to feed an army. Now one is out of the house, the other isn’t home most of the time and husband works evenings. We don’t have company like we used to before Covid, so unannounced guests happen rarely.
I have to be conscious at all times about what I’m cooking. First I had to admit that my perception of how much food I needed was just wrong and could not be trusted. I started using recipes - even for things I know how to make- purely to reference serving sizes. And when all else failed, however much I felt I needed to make, I’d just make half of that
It took some practice but now I make reasonable sized meals and have few leftovers.