It's not easy to find a way to express harmony without name it, in three syllables.
Generally, I tend to avoid to name abstract concepts, but there is a drawback: the feeling evoked in the reader is almost certainly different from mine.
This is fine for me, but maybe another haiku author wants more precision.
My take on this one could have been something like that:
at the cusp
of the turning tides -
tranquil breath
oh yes! That is lovely! thank you!