One early theme in Ann Voskamp's book “One Thousand Gifts” is that of thanksgiving (in tandem with joy and grace). So I dutifully sit down to look for all the positive things in my life, and as I suspected, I find very many. To list them helps me to see just how many there are. I would encourage you to do likewise.
So let's start with the obvious causes for thanks, such as life, health, family members, and most importantly of all, the knowledge of the God who created me. If I'm not thankful for that, then I'm not