Das Leben (life)
+ Die Lüge (lie)
= Die Lebenslüge (life-lie).
A Lebenslüge is a lie we tell ourselves in order to make existence bearable, whether to achieve some particular goal or just to get out of bed in the morning.
The word was popularized first in Norwegian, appearing in Ibsen's The Wild Duck as livsløgn. German translations of the play rendered it Lebenslüge, whereupon it entered general speech in that country as well.
When attributed to an individual, a Lebenslüge is a grand self-delusion – think Don Quixote. At least in the German discourse, Lebenslügen are often attributed to nations as well, referring to a false conception of the past that forms a vital part of the national self-image. For instance, historians have accused postwar Austria of perpetuating the Lebenslüge that they were wholly a victim of Nazi expansion during the Second World War, a narrative of collective innocence that ignores the complicity of many Austrians with Hitler's regime.