It is told of the Holy Grandfather of Radoshitz that in his youth, before he became a rebbe, he was terribly poor and often had' nothing to eat.
One year, after he had eaten nothing from Yom Kippur to the day before Sukkot, his wife sold a jewel she had and bought candles, challah, and potatoes for the festival.
When he saw the candles and challah on his return from the synagogue, he was very happy, recited the Kiddush, washed his hands, and sat down to eat.
Being very hungry, he ate ravenously, until he suddenly stopped and said to himself: "Berl, you are not sitting in the sukkah but in the plate!"
Someone can be tending to the most basic needs of his body and with conscious intent be observing the mitzvah of eating in the sukkah, yet still be sitting in the dish and not in the mitzvah.
–Rabbi Adin Steinsaltz
From Opening the Tanya by Rabbi Adin Steinsaltz