If I serve myself, or if someone who knows me well serves me, then I usually clean the plate. If I'm at a restaurant or something, then I almost always leave something left. Though I can often eat a lot cumulatively, I can't always eat a lot in one sitting.
I was brought up in the "eat everything on your plate" home. However over the years I learned it is OK to leave something behind. In many cultures it is a sign the cook gave you more than enough. If you clean your plate you would be saying you did not give me enough to eat.
Almost always, I finish the lot. Including the skins of the smoked mackerel fillets I had today. I don't like to waste food anyway, but cooking for myself, I know how much to cook.
A former neighbour, Janet, once told me she had a 'phone call from the local Council, surveying the efficacy of their waste-collections. The woman asked Janet that they'd noticed her food-waste bin was always empty - how come?
"We don't waste any. We don't over-buy and what is inedible are either fruit and veg bits that go on the compost heap; or bones, and after I've boiled them down to make stock they can go in the ordinary rubbish!"
"What about what's left on your plates?" the Council lady persisted.
"We don't leave any - we all know what we each like, and how much!" Janet said she had to explain.
The Council woman was most surprised. She could not understand a family not wasting food!
(The collected food waste is sent for composting.)
Benedict Arnold 