“When you go through a breakup, especially one that’s unexpected, your body may register it as an emergency and go into “fight-or-flight” mode. Being in this state triggers the release of hormones that can prepare your body to stay and deal with a threat or to run away to safety. It can also trigger a rapid heartbeat or trembling.
Our muscles tense, we lose our appetite, we may experience [gastrointestinal] disruption, and we’re likely to have trouble falling asleep. Being in this physically hyper-vigilant state over a period of time can lead to headaches, stomachaches, and muscle soreness”
by Dr. Kristin Bianchi