be chasing your tail

be chasing (one's) (own) tail

To be taking action that is ineffectual and does not lead to progress. Refers to how a dog can exhaust itself by chasing its own tail. Come on, Bill, go to sleep. You're just chasing your tail at this point, but you might have a breakthrough with the research if you take a break from it. I've been chasing my tail on this project because so many components of it are just not working out.
See also: chase, tail

be chasing your tail

or

be chasing your own tail

If someone is chasing their tail or is chasing their own tail, they are using a lot of time and energy but not achieving much. I'm more relaxed now. Before, I was chasing my tail like some sort of lunatic. I've been chasing my own tail all these years.
See also: chase, tail