According to a recent study if a person has a steady heartbeat when he is worried about something than he might be more susceptible to stress. The research conducted by the Concordia University showed that a less variable heartbeat when worried makes a person highly stressed later on. 'At rest a more variable heartbeat is a good thing. It shows that your parasympathetic nervous system is hard at work. That is the system that is responsible for the 'rest-and-digest' state of being - the opposite of 'fight-or-flight'' explained psychology professor Jean-Philippe Gouin. The rest-and-digest phase puts you in a calm