I love to read quotations about gratitude or thankfulness. They are so eye-opening most of the time, pointing me to the fact that it is so easy to forget to be thankful. It's so easy to fall into the trap of entitlement, which prevails our culture. Gratitude, like the quote above implies, is really a soul/heart-type-of-matter.
It won't do us harm to take a moment and ask ourselves why we're not more grateful than we should be.
When you rise in the morning, give thanks for the light, for your life, for your strength. Give thanks for your food and for the joy of living. If you see no reason to give thanks, the fault lies in yourself. - Tacumseh