as a dog returns to his vomit, so a fool repeats his folly

as a dog returns to his vomit, so a fool repeats his folly

Foolish people are apt to repeat their missteps. A: "I can't believe Sarah is going skiing again, after she broke her leg the last time." B: "Well, as a dog returns to his vomit, so a fool repeats his folly."
See also: dog, folly, fool, repeat, return