Someone who smiles too much with you can sometime frown too much with you at your back.

Don't let your teeth make you lose respect by permanently keeping them opened for the sake of being friendly.

Don't cry for someone who would love smiling when your tears are flowing.

The only known technique to an imitator is to steal and rephrase, then with a mischievous smile, he said, "i did it", without any confidence and prove.