(one's) good deed for the day
Some especially good, kind, or generous thing one has done. Sometimes used ironically or sarcastically to suggest that a certain deed is not good or not as good as someone thinks. Wow, so you went all the way across town to deliver the missing wallet to its owner? That's your good deed for the day! It's like the guy thought he was doing his good deed for the day by pointing out my mistake to me. A: "OK, so you helped an old lady cross the street—that's your good deed for the day. You can go back to being your usual indifferent self now." B: "Why, thank you, I will."
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