Sometimes I hear someone talking to their children and comparing them unfavorably to another child. This really makes me cringe, especially when it's me who's doing the comparing. What does that sound like to the child?
"Lucinda, if you practiced your piano for 2 hours a day like Trina Snarkton does, you'd be a much better player" can become "I wish you were more like Trina Snarkton " which isn't all that far (to a young mind) from "I wish Trina Snarkton was my daughter instead of you."
Imagine if our children did that to us: "Mom, I wish you played dolls with me more, like Mrs. Jackhammer does with Cosgrove." Or our spouse: "Honey, why do you always wait till April 13 to do the taxes? Norton Fladwhopper has his done by March 1 every year!" What's the likely response? A defensive "I'm not Mrs. Jackhammer." A muttered "Maybe you should have married Norton Fladwhopper instead!"
Imagine the wrath of a wife hearing from her husband "Dear, you ought to make your apple tartlets like Felicity Warfnoggle does!"
We all have room for improvement. We all know someone who does something better than ourselves, our spouses, or our children. We need to give encouragement, not unfavorable comparisons, if we want to see improvement. If we see someone with a quality or characteristic we'd like our child to have, we can talk to him or her about it without bringing in the person who has the desired quality.
Oh, can you tell we've been listening to and reading Mrs. Piggle-Wiggle lately?