I've been noticing a sharp pain in the left side of my neck, possible main artery. happens when i get upset, anxious or mad. what could this be?

One possibility: Many people express anger, upset and anxiety through tensing muscles - especially muscles of the upper back and neck. That can cause pain. To keep from getting so upset try this: reath in slowly & deeply through your nostrils. Fill your lungs with air (but not to the point of discomfort). Hold for a count of five then slowly begin to exhale through an open mouth. Repeat at least 12 times, longer