We are chipping away at the infinitely complex human brain and its emotional centers, but I sincerely doubt we will ever be able to fully comprehend all the interacting systems. So, in the meantime, eat healthy with lots of colorful magnesium / sulfur rich veggies, zinc rich foods, and healthy fats / essential oils (including a good amount of omega-3), exercise regularly, share often within a nurturing relationship (verbally and physically), strive for adaptability and resiliency in your reactions, and pray regularly. And don't watch the news, it's far too depressing. Instead, learn about your world with your own eyes and through the eyes of trusted friends.
"This stimulation shunts tryptophan from production of serotonin and melatonin to the production of a disruptive excitatory compound called quinolinic acid, at the expense of a more regulatory compound called kynurenic acid...
Natural NMDA modulating agents include magnesium, zinc, taurine, glycine, N-acetylcysteine, and phenibut or GABA. Food additives, on the other hand, such as MSG (often hidden under one of these pseudonyms) stimulates the NMDA receptor in a toxic way that can cause unpredictable neurologic symptoms."