Be chasing (one's) (own) tail American British verb phrase
Used when someone is busy to do a lot of things but achieve little and do not lead to progress
I have been chasing my tail all day, but I haven't finished any tasks.
Used when one wishes to engage in sex with someone
They admitted that they were chasing tail in the bar last night.
The verb "be" should be conjugated according to its tense.
Put an end to a bad experience or situation in an especially negative way, usually a series of unpleasant events
I argued with my wife this morning and failing in negotiating with my customer has put the tin lid on my bad day.