get something off one's chest
to unburden oneself; to confess something; to criticize or make a personal complaint to someone. You will feel better if you get it off your chest. I have to get this off my chest. I'm tired of your rudeness to me!
get (something) off (one's) chest
To vent one's pent-up feelings.
get (something) off one's chest, to
To unburden oneself of a secret, criticism, worry, or the like. The London Daily Chronicle of 1902 is cited by the OED: “To deliver a message to the world or to express the individual personality—to ‘get it off your chest’ is the horrid vulgar phrase.”