The Greater Good Science Center at UC Berkeley has an excellent article describing the science: https://greatergood.berkeley.edu/article/item/why_we_love_music. My post of Joy to the World describes my response to the music, and they give the science on why.
Thanksgiving Day has so many special aspects that highlight how much we have to be grateful for. You get to pick your focus- family, friends, football, feast, foliage and so much more. It is easy to get swept up in the planning, or to feel sadness if something from the past is no more- Taking a few moments to get quiet, and focus on what is going right can turn that around.