It's a cliche of parenting: parents are first horrified to hear something their child said and then experience a second horror when they realize that their child is just parroting back something that they themselves have said. Luckily, the same type of realization can happen with something really nice:
Pete: Can I have more cereal, please, Mama?
[I put more cereal in his bowl.]
Pete: Thank you! That's awfully nice of you!
I was first really happy about his manners (which aren't always quite that good), and then I realized that I could hear "That's awfully nice of you" in my own voice. It's good to have moments of reassurance that we're doing some things right. As Pete might say, Good job, MamaPapa!