You cannot figure out because you cannot remember.
How are you Luce in these days? You're getting very clear in your words,

A song of joy in a midnight,
where fairies flutter
a dance my eyes witness
for the first time.

They sway and move
so effortlessly like the
brush of an artist
to their homes within
water lilies.

Sometimes ideas and poetry take time to work themselves out. You may have a word, a phrase, or even a decent fragment of poetry that you keep coming back to, but you are not sure where it is headed. Save the fragment. Set it aside for now and come back to it a week, a month, or several months later. When the time is right, the fragment will make sense and the words will come. You will work out what you want to say given time. For my poem “My Pen” I originally wrote the first three lines two years before I was ever able to articulate and put to words exactly what I was feeling and what I wanted to say.

I hope it does not take you so long to work this piece out. I like the start you have to the poem, and I can see a lot of potential in it. You could take the poem in so many directions from where you have started with this first stanza. It could take a very literal descriptive spin about the firefly you mentioned in the tentative title, or it could just be the intro to a much deeper metaphorical meaning. Keep at it. If you have no further inspiration for this piece set it aside, but don’t give up on it. Come back to it and see where it takes you.