1) Figure out exactly what triggered your anger. Was it the rude comment your coworker made during lunch?
2) Consider any other emotions that may be behind your anger. Do you feel embarrassed about the snide remark she made in front of other people? Are you really unhappy with your job but afraid of change, so you don't look elsewhere?
3) Plan a course of action to fix the situation. Have a conversation with your coworker to find out why she made that comment. Check job boards and see what other opportunities are out there.
A good rule: Always "sleep on it" or take some time before reacting. The physiological effects of a triggered emotion affect how you think, says Dr. Lamia. Giving yourself a few hours can help you clearly think through what's going on and the best action to take.