Definition
Used to describe a problem or issue that is not real and exists only in someone's imagination.
純屬虛構；庸人自擾
She keeps feeling like there are ghosts in the room, but I think it’s all in her mind.
她一直覺得房間裡有鬼，但我認為這都是她想出來的。
He was convinced that everyone was talking about him behind his back, but it was probably all in his mind.
他確信每個人在背後談論他，但這可能都是他想出來的。
When I told him I couldn't hear any noise, he realized the sound was probably all in his mind.
當我告訴他我聽不到任何聲音時，他意識到這聲音可能都是他想出來的。