Regarding regret

From a former coworker of my father's, a couple of decades ago:

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I thought of you today and how you would laugh at the funny things my daughter said so I have to tell you one that happened today.

She is in summer camp and today they are performing in a little play. She's been telling us the last week that she doesn't want to be in this play because she feels silly but we still feel she needs to be there with the rest of her class. Today she put up a real fit and didn't want to go to camp because of the play but Tom [her father] took her there anyway and this is what she said when she arrived "I am going to regret this the rest of my life, and I don't even know what regret means".