Background: Moss was born in London, son of Alfred Moss, a dentist of Bray, Berkshire, and Aileen (nee Craufurd). He was brought up at Long White Cloud house on the right bank of the River Thames. His father was an amateur racing driver who had placed 16th at the 1924 Indianapolis 500. Stirling was a gifted horse rider as was his younger sister, Pat Moss, who became a successful rally driver and married Erik Carlsson.
Context: Although ostensibly retired from racing since 1962, Moss did make a number of one-off appearances in professional motorsport events in the following two decades. He also competed in the 1974 London-Sahara-Munich World Cup Rally in a Mercedes-Benz, but retired from the event in the Algerian Sahara. The Holden Torana he shared with Jack Brabham in the 1976 Bathurst 1000 was hit from behind on the grid and eventually retired with engine failure. Moss, at the wheel of the Torana when the V8 engine let go, was criticised by other drivers for staying on the racing line for over  2/3  of the 6.172 km long circuit while returning to the pits as the car was dropping large amounts of oil onto the road. He also shared a Volkswagen Golf GTI with Denny Hulme in the 1979 Benson & Hedges 500 at Pukekohe Park Raceway in New Zealand.  In 1980 he made a comeback to regular competition, in the British Saloon Car Championship with the works-backed GTi Engineering Audi team. For the 1980 season Moss was the team's number two driver to team co-owner Richard Lloyd. For the 1981 season Moss stayed with Audi, as the team moved to Tom Walkinshaw Racing management, driving alongside Martin Brundle.  Throughout his retirement he raced in events for historic cars, driving on behalf of and at the invitation of others, as well as campaigning his own OSCA FS 372 and other vehicles.  On 9 June 2011 during qualifying for the Le Mans Legends race, Moss announced on Radio Le Mans that he had finally retired from racing, saying that he had scared himself that afternoon. He was 81.
Question: How did he scare himself?. Whats the answer?
retired with engine failure.