Appreciation is a form of Gratitude, which is a form of Love. And properly directed Curiosity - a joyful and playful engagement with the world - is the active mental state that goes with this, along with peace - the more quiet mental state that also accompanies appreciation.
Appreciation, Gratitude and Curiosity are the fundamental baseline mental-emotional state of all animals, but for some reason humans have made them special... And by "special" I mean that they have become relatively uncommon experiences instead of being the mental-emotional place from which we experience and interact with the world. The fact that the body - the brain, the physiology, everything - has evolved to be optimised for these mental-emotional states means that they are very important for all aspects of health, as well as improving learning, mental focus, and inter-personal communication.
Most importantly for our purpose here, they also provide a means by which the body's sensory system can be programmed to recognise that the world is safe - as opposed to expecting that the world is dangerous. So Appreciation, Gratitude and Curiosity are very useful tools in the treatment of trauma and in regulating the Autonomic Nervous System.