The smaller the bag, bottle or bowl, the less you will eat.
Use a smaller plate.
The Portion Size Illusion is a new variant of an old classic illusion called the Ebbinghaus illusion, in which a circle surrounded by smaller circles looks bigger than the same circle surrounded by bigger circles.
It shows that, to your visual system, everything is relative. So you feel like you are indulging in a bigger portion of food, but really you are just using a smaller plate.
If you feel full, STOP eating! Don’t feel bad for wasting food. Next time, dish up less and if you are genuinely still hungry, you can always go back for seconds!