"R' Achai ben Yoshiya says: One who purchases grain from the market [to make his own flour], to what can he be compared? To a baby whose mother died and they pass him from door to door among wetnurses and he is not satisfied. One who buys bread from the market, to what can he be compared? It's as if [his grave] is dug and [he is] buried. One who eats from his own [which he grew] is like a baby who is raised at his mother's breasts.
"He used to say: At the time that a person eats from his own, his mind is settled/tranquil for him. Even one who eats from his father's and from his mother's and from his children's, his mind is not settled/tranquil, and you don't [even] need to mention if he eats from that of others."
From Avos de'Rabbi Nasan, brought to my attention "Food For Thought," the Hazon sourcebook.