mug's game
Noun
Meaning
a futile or unprofitable endeavor
Source: WordNetHypernyms
Examples
As things are, and as fundamentally they must always be, poetry is not a career, but a mug's game. No honest poet can ever feel quite sure of the permanent value of what he has written: He may have wasted his time and messed up his life for nothing.
I am not interested so much in behaviour from which you infer consciousness because that is a mug's game. I don't know whether you're conscious. I take a good guess that you are and you can take a good guess that I am but it's not something you can prove. We can't work out what someone else feels.