in one's own world

1. Also, in one's own little world; in a world of one's own. In deep thought or concentration. For example, Luanne was really in her own world at the meeting this morning, or Like many mathematicians, Bill lives in his own little world, or Bob's in a world of his own when he's listening to music. [Late 1500s]

Example Sentences

What they did not admit was that such things never having occurred in one's own world, they had been mentally relegated to the world of newspaper and criminal record as things that could not happen to oneself.

From Project Gutenberg