A nervous habit, also known as a TIC, is an unconscious, repetitive behavior that is often associated with anxiety or stress. Tics can range from mild to severe and can include facial twitches, head jerks, shoulder shrugs, and other physical movements. They can also include vocalizations such as throat clearing, humming, or repeating words or phrases. Nervous habits are usually harmless, but can be disruptive and embarrassing in social situations.