Oh, don't worry - it's not "leaving" in a sad way. I just thought that there should be a point at which Josh realises that it's time for him to leave the WH and have an actual life with Donna; that

Hell, we spent more time together when you were my assistant than we do now.

and it's not what he wants any more.

There may be a proposal in there somewhere...

Sadly, it's not a lot more than a set of notes and bits of dialogue :(