Little Things make a big difference. Sometimes when you're facing what looks like a mental brick wall, you can take it apart in little ways—brick by brick or, rather, thought by thought. Gratitude is one of the thoughts that helps dismantle those walls.
When I was about 16 or 17, I decided to read the book of Psalms in the Bible. As I read, I noticed how the listeners (the Psalms were probably recited or sung) were occasionally urged to "magnify the Lord." Here's one example: "Let such as love thy salvation say continually, Let God be magnified." Ps. 70:4.
When we don't see good for what it is —God Himself— we wind up settling for a limited amount of it.
