Honestly, I never know how to respond to this question. Maybe I'm overthinking it (I do that a lot). The question implies to me that thanks needs to be specifically directed, such as "to" a person, or entity, and I am not a "believer."
An obvious answer seems to be happy to be alive, which I most definitely am not. Existence has forever been miserable and tortured to me.
I guess the best I can do is say that since I am stuck here I am thankful that I am able to wipe my own caboose after I crap and don't have to suffer the indignity of someone having to do that for me.