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. I'm chasing my own tail trying to talk to a person at the cable company. I've been on hold for an hour now!

be chasing tail

1. To be very busy or working very hard at some task but accomplishing little or nothing as a result; to be engaged in some fruitless or futile task or endeavor. Likened to a dog running in circles trying to catch its own tail. I'm chasing tail trying to talk to a person at the cable company. I've been on the phone for an hour! Come on, Bill, go to sleep. You're just chasing tail at this point, but you might have a breakthrough with the research if you take a break from it. I've been chasing tail on this project because so many components of it are just not working out.

2. slang To be pursuing or seeking out sexual activity with someone. (Usually used by men to refer to women.) My brother is always chasing tail in bars around town. I've been chasing tail for years. Now, I'm ready for an actual, meaningful relationship. I know that you're just chasing tail—that, if I say no, you'll just take some other girl home with you.