Very shocked or distraught. I was beside myself when I found out I'd been rejected from my first-choice school. Honestly, we've all been beside ourselves since the funeral.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
beside oneself (with something)
Fig. in an extreme state of some emotion. I was beside myself with joy. Sarah could not speak. She was beside herself with anger.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
In a state of extreme agitation or excitement, as in She was beside herself when she found she'd lost her ring, or Peter was beside himself with joy-he'd won the poetry award. This phrase appears in the New Testament (Acts 26:24): "Paul, thou art beside thyself; much learning makes thee mad." [Late 1400s]
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.
beside oneself, to be
To be distraught with worry, grief, anger, happiness, or some other strong emotion. The expression appears in the King James Version of the Bible (Acts 26:24): “Paul, thou art beside thyself; much learning makes thee mad.” It uses the adverb beside in an older sense, meaning “outside of,” so literally the phrase means “outside of oneself,” the self in question being one’s mental faculties.
The Dictionary of Clichés by Christine Ammer Copyright © 2013 by Christine Ammer