One question, have you always had that same mindset or did it develop with age? It took me many years to get into the gratitude thing. As a child I thought myself cursed with little to be grateful for. A wise nun once told me that every situation is just that, neither positive or negative and it's your reaction to it that determines the outcome. I pondered this for some considerable time before realising that I was author of my own woeful tale and giving myself a good kick in the arse.
As an adult mostly, although I learned it along the way like most I suppose...the harder the lessons the more I learned. (Had some pretty difficult lessons in life, tough situations.)
I like what that nun told you, a valuable lesson to learn in life for sure. I suppose the older we get the more we pay attention to the experiences, the more mature we are, and so they stick with us a little better.