Off The Rails Meaning

Example : 2009‎ Jul 13, Ed Bentley, “Lenin 1, Tsar Nicholas 0 – but Sheremetyevo-3”, Moscow News:  ... but the plan came off the rails when infuriated Communists called it "ideological provocation" and warned against "kindling political confrontation2009‎ Jul 10, Jenny Johnston, “You won't catch us going to rehab: So have the young stars of Harry Potter turned into superbrats?”, Daily Mail:  I reckon it's pretty astonishing that none of us did go off the rails. There really was no telling how any of us would deal with the pressures and the fame.