Three Daughters

There was a father who was very proud of his three daughters. Every night he took a stroll around the house to make sure everything was all right. One night when he was doing his stroll, he could hear laughter coming from his youngest daughter's room. He stood there for a while and thought about this, but reached the conclusion that he could always ask her tomorrow, instead of bothering her at this time of the night. When he reached the window of his second daughter, he could hear her crying. He thought about this too, but ultimately he decided to ask her tomorrow and continued. There were no sounds at all coming from his oldest daughter's room, and he then went to bed, satisfied. The next day, when they all were gathered around the breakfast table, he said to his youngest daughter "I heard you laughing last night, as I walked past your window. Why was that?"
She answered "That's because you taught me to laugh when someone was making me happy..."
He then asked his second daughter "I heard you crying last night, why was that?"
She answered "That's because you taught me to cry when someone was making me hurt..."
He then told his oldest daughter "I didn't hear anything from you..."
She said "That's because you taught me not to talk with my mouth full..."