" Serotonin helps with impulse control, willpower, and resilience. Dopamine is important in enjoyment and habits. Norepinephrine modulates focus and concentration. Oxytocin is essential to close relationships. Other neurotransmitters are important too, like GABA (antianxiety), endorphins (elation and pain relief), and endocannabinoids (appetite and peacefulness). Other chemicals, like BDNF, help grow new neurons, and even proteins in the immune system play a role. "

― Alex Korb , The Upward Spiral: Using Neuroscience to Reverse the Course of Depression, One Small Change at a Time