Holding a grudge produces cortisol and diminishes oxytocin. Oxytocin is the hormone responsible for that ‘good feeling’ when somebody gives you a hug. A mother produces oxytocin when she Breastfeeds her infant. In turn the baby also produces oxytocin as it feeds. High cortisol levels are responsible for slow healing, the destruction of healthy muscle and bone, weak immune systems and poor mental function. So do NOT hold grudges, help a friend out and share.