Of the seven deadly sins, surely it is pride that most commonly afflicts the gardener.
Don't eat anything your great-grandmother wouldn't recognize as food.
Nature abhors a garden.
What an extraordinary achievement for a civilization: to have developed the one diet that reliably makes its people sick!
Don't eat any foods you've ever seen advertised on television.
We used to eat economically. One of the things that happened is that we lost the cultural skills that used to allow people to eat well cheaply. For example making three or four meals from a chicken, rather than buying chicken breasts.