How much should I eat or does it vary for each person?

From my non-professional view, I think it varies a lot depending on the person, regardless of this, there is a trick to not over-eat, this is:
I know when I’m going to get full or not, so I just eat until a bit before of being full. Also is important to say that you can get full with healthy food, just not before bed, it steals quality on your sleep.