lose oneself in
Become deeply absorbed or involved in, as in Doctors are notorious for losing themselves in their work. This expression alludes to becoming so absorbed as to forget oneself. [c. 1600]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.