Telltale Mouth

The mouth is a barometer of how happy or angry a person is. If someone is grimacing, or tightening or pursing her lips, she is usually frustrated or annoyed with you. If her annoyance with you persists, her facial expression may turn to disgust as she raises her chin and upper lip and wrinkles her nose. If she is unhappy or sad being with you, her face will appear expressionless (with the exception of her eyes and surrounding muscles) and her lower lip will turn downward. If she is nervous around you, you may notice her sucking, biting, chewing, or licking her lips a lot. She may smile nervously, wherein she immediately smiles (often at inappropriate times) and then resumes her normal facial expression.

This is what physically happens to your face when you express the following emotions.
Happiness
Smiling mouth
Cheeks raised
Lips parted
Jaw slightly dropped
Wrinkles around eyes
Eyes relaxed and narrowed

Sadness
Eyebrows raised
Forehead wrinkled
Lower lip depressed—turned
downward
Upper eyelids lowered

Anger
Eyebrows lowered
Hard stare
Lips raised
Open mouth

Disgust
Lower eyelid pushed up
Upper lip raised
Nose wrinkled
Open mouth
Chin raised
Eyebrows lowered
Eyes tensed and narrowed

Surprise
Eyebrows raised
Upper eyelids slightly raised
Mouth open
Jaw drops

Fear
Eyebrows raised
Upper lids raised
Lips stretched
Mouth open
Tense, open eyes