None of the groups I've been to have said that phrase.
When I seriously am practicing gratefulness, I tend to find a lot of things I'm thankful for that I wouldn't have expected.
It's not that happy people are thankful. Thankful people are happy.
How Gratitude Can Change Your Life 
I wouldn't wish illness or difficulties on anyone. I fight and hate having them in my life, but that's never done any good. When I start being thankful for all the little things in my life, the transformation begins. For this transformation, I am also thankful. Without my illnesses I would not be finding this, so in that I have, at the best of times, been thankful even for that.
Thank you very much for posting this. I've been struggling lately and this helps point me back to what has worked for me, time and again.