Chain chewing gum. When you're anxious about something and start maniacally chewing one gum after another (normally dedicating a few seconds to each gum, not taking all its flavour).
It can get addictive when you're really nervous. Its like soft drugs for kids. Afterwards, you feel funny.
Don't try it with Big Red though.
After his chewing gum chain, Jake felt sick and twice as nervous.
Jessica chain chewed a whole packet of Big Red and her mouth felt like burning shit the rest of the day.