all in one's head

idiom

: in one's imagination : not real
The problem is all in his head.

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all-in-one
all in one's head
(all) in one whack
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“All in one's head.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/all%20in%20one%27s%20head. Accessed 23 May. 2025.

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