1
general::
Overlook, fail to take into account, as in We must not lose sight of our main objective, or Beverly never lost sight of her humble beginnings. This metaphoric expression alludes to physical sight. [Early 1700s] For an antonym, see BEAR IN MIND.
American Heritage Idioms
2
general::
Phrase(s): lose sight of someone or something
1. Lit. to have one’s vision of someone or something fade because of distance or an obstruction. • I lost sight of Alice as she walked into the distance. • We lost sight of the ship as it sailed out of the harbor. 2. Fig. to forget to consider someone or something. • Don’t lose sight of Alice and her basic contributions. • Don’t lose sight of the basic value of the land on which the house sits.
McGrawhill's American Idioms And Phrasal Verbs