고 그만두다

and then quit

"-고" chains an action to 그만두다, "quit, stop, give up". The lines are mostly about leaving a job: serve the term out and step down, quit because something hurt, work until 2007 and then quit, a company you dread going to but haven't quit. It also covers giving up mid-effort — not being able to keep holding your breath and stopping. 그만두다 is quitting for good, unlike 멈추다, which is just coming to a halt.