Doctor Julian Jaynes wrote about a woman who talked daily to her long-dead grandmother, who she saw sitting in a chair each morning.
As far as the doctor could tell, the woman never suffered any ill effects from this. In fact, she readily accepted that it was a hallucination, which didn’t bother her at all.
She just found the conversations, and her grandmother’s advice, helpful.
Advice From Ghosts
Hallucinations aren’t necessary, but why not have a conversation in your head with somebody helpful?
Albert Einstein might even give you a creative idea or two.