We're about to get a little sciency here...but not too much!
Gratitude is linked to the your Medial Prefrontal Cortex (PFC), the front part of your brain.
Your medial prefrontal cortex sets context, defines the meaning of a situations and is extremely linked to gratitude. The PFC allows us to take experienes and frame them as positive or take the same exact experience that we are forced to do or don't want to do as negative.
Think of a hard training session - your PFC sets the context as to whether you are doing this for something more or a larger goal, or it just sucks to do it. Gratitude is a mindset that activates the PFC and in so doing so sets the context for your experience!
So much so that you can get amazing health benefits and truly enjoy more activities.
It won't happen right away, but you can change the circuitry in your brain to frame experiences to be more enjoyable and to have an overall higher disposition to gratitude.