Thankfulness is a choice, and it is about perspective.
If you are not thankful, then perhaps you are not seeing the complete picture of your life.
Are you bitter about a job with pressure, deadlines, and quotas, or are you thankful that you have a job? Are you bitter about family relationships, or are you thankful that you have a family? Are you bitter about your living situation, or are you thankful that you have a roof over your head? Are you bitter about your health, or are you thankful that you are alive another day?
Thankfulness, like gratitude, is a choice. Thankfulness should come through any circumstance, not just when things go your way.
Do you notice that one or more of your co-workers always seem to have a good attitude? I doubt it is because their life is perfect and everything for them is going great. Instead, I propose that they have simply decided to be thankful, regardless of their circumstances.
An old saying comes to mind as I write this: “I cried when I had no shoes, until I met a man who had no feet.”