“Everybody has a plan until they get punched in the mouth.” People quote it about plans that fail when real events go against them. It is credited to the boxer Mike Tyson. His own words were slightly different.
In August 1987, before a fight with Tyrell Biggs, Tyson told the Associated Press: “Everybody has plans until they get hit for the first time.” The wording with “punched in the mouth” appeared in a newspaper column in 2004. Quote Investigator concludes that the saying belongs to Tyson.