The question is why do you repeat it?
A)You think it works that way
B) You don't like a song to be that short.

I can't argue with A). But if it's a case of B) consider that if a song is well sung, short can be good. And failing that, this song in particular has lots more verses:
I once loved a young girl...
It's deeply I loved her...
According to promise...
Farewell to you Molly...
...to mention just the ones I know. Any of these might be considered as an alternative to repetition.