Tilting at windmills

Means wasting time and effort with imaginary obstacles and first appears in the form of ‘fighting with windmills’ from the mid-17th century. The expression derives from Cervantes Don Quixote (1605) when Don Quixote mistook windmills for giants with flailing arms and wanted to tilt at them (joust) with his lance. The exact phrase tilting at windmills first appeared during the 19th century but the figurative meaning of wasting time and effort with imaginary obstacles was well established by then.