A Deteriorating Soul, Featuring Nostalgia.
Nostalgia and anger, etymologically speaking, are derivatives of pain. Pain is a wrecking force by itself. It's an unguarded monster that eats souls for a living. Nostalgia and anger are the gods that shredded the titan called Pain and scattered his remains in the deepest part of a human being and fought for the position of the wrecking ball. While both of these gods are dangerous, one of them is the god of all the other gods. While, like in 'Inside Out', everyone has a different leader, here is my take.
Nostalgia, derived from the Greek words 'NOSTOS' and 'ALGIA', talks about the yearning or the pain felt from being far from home. Homesickness, if you will. Now, home (by home, in this context I mean the memories we sigh about) is an abstract concept people try to organise and understand. It is a ball of chaos we try to untangle because home, that apple dangled in Tantalus's face, we think is for eternity. Maybe, just maybe, home is a memory you can't revisit in real time. Home is the phantom leg we lost in an accident, we think it's there and then we open our eyes and, really, it's not. Yearning for a home that's not there in the physical world, paining for something you don't understand, every unregulated sigh of 'those were the days' drive a person mad and the only thing that can restore a person's sanity is a poorly recreated material of home that leads to dissatisfaction.
Dissatisfaction is a one way descent to extremities like frustration that, sometimes, go beyond just angrily kicking off the blanket on your bed and then sobbing in your pillow. Sometimes it's losing your mind over a sound piercing through silence, and lose your mind you do. Insanity, often, is one of the worst fate any animal that breathed on this land will endure. Insanity is death before death itself. It's the mother of all chaos and definitely isn't half as fun as your average perception of chaos is. This whole route nostalgia, in unimaginably extreme cases, takes is frankly overdramatic but there will be a bright yellow sign with the word 'caution' highlighted in bold.
Point is, if my phantasmagoric perception my gruesomely imaginative mind conjured is anything to go by (take it with a whole sea of salt), nostalgia is a dominoes of a deteriorating soul waiting to happen. While anger and nostalgia end up in the same sea, the journey it takes, the path it flows through makes nostalgia a tad bit more dangerous and worse, longer.