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
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

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
Collins COBUILD Idioms Dictionary, 3rd ed. © HarperCollins Publishers 2012
See also: