the first flush of youth, enthusiasm, etc.

the first flush of (something)

The beginning or early stages of something. Of course they're happy now—they're still in the first flush of marriage!
See also: first, flush, of
Farlex Dictionary of Idioms.

(in) the first flush of ˈyouth, enˈthusiasm, etc.

when somebody is young or something is new: By then, he was no longer in the first flush of youth. In the first flush of enthusiasm, we were able to get everyone interested in helping.
See also: first, flush, of
Farlex Partner Idioms Dictionary
See also:
  • be in the first flush of (something)
  • flush
  • the first flush of (something)
  • in the first flush
  • in the first flush of (something)
  • come to an understanding
  • understanding
  • flush away
  • Flushing
  • two of a kind