To behave in an impolite or unrestrained manner. Sure, sometimes I forget myself and snap at the kids, but doesn't every mother?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
to forget one's manners or training. (Said in formal situations in reference to belching, bad table manners, and, in the case of very young children, pants-wetting.) Sorry, Mother, I forgot myself. John, we are going out to dinner tonight. Please don't forget yourself.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
Lose one's reserve, temper, or self-restraint; do or say something out of keeping with one's position or character. For example, A teacher should never forget herself and shout at the class. Shakespeare used it in Richard II (3:2): "I had forgot myself: am I not king?" [Late 1500s]
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.