be over the moon

be (or jump) over the moon - be very happy.
feeling, showing, or expressing extreme joy; very pleased

This person was lean and brown, his eyes were extremely clear; he held himself very straight and looked fit to be over the moon. (J. Galsworthy, ‘The Little Man and Other Stories’, ‘The Perfect One’

‘It's only a few weeks since you were over the moon about Davina.’ ‘Well, now I'm not.’ (P. H. Johnson, ‘The Survival of the Fittest’, part VI, ch. V)