all in (one's) head

all in (one's) head

Not substantial or real; having been imagined or invented. I don't know why you think I don't trust you. I can assure you that it's all in your head.
See also: all, head
Farlex Dictionary of Idioms.
See also:
  • don't get me wrong
  • (I) won't tell a soul
  • don't bet on it
  • bank on
  • banking
  • don't give up the ship
  • don't beat a dead horse
  • don't cry before you are hurt
  • don't count your chickens