In recent times (among others) reading Frankenstein (written by Mary Shelly) has opened my eyes to see things that I don't necessarily acknowledge in my day to day life.
It is not a lesson learnt or anything major. Some lines in the book opened my eyes to the fact that nature and life are wonders that no money can ever earn. If you are a monster plagued by deformity and unloved by anyone (like the monster in the book), you start to see humans and their good ways, their bonds of love and family, simple things that every person is endowed with by right, and realise that these things are priceless.
The privilege to have someone look on you with love, to have someone to just talk to, to wake in the morning and see fresh day with plans ahead can never be bought. They come to us free.
Maybe that is why we take them too lightly. Maybe humans have become so screwed, they begin to believe that things bought by money or earned are worth more than things that come free.
Maybe only when we are robbed of things we used to have we understand how priceless they were.