The speaker is describing what it feels like to fall in love with someone who may not love them back. The fall in the title works as a single extended metaphor: each shared moment pulls the speaker a little further down, and the whole poem is the drop. Speaking openly, giving gifts and writing poems all make the speaker more vulnerable, and the poem admits this early, saying that opening up means "leaving myself open to pain."
The mood starts out hopeful and tender, with the speaker praying to be caught and accepted. Then it tightens. "The ground closing in" brings a sense of dread, and the speaker keeps looking up, still hoping for love even as the end approaches. The last lines are blunt and painful: the speaker hits the ground. The poem doesn't say exactly why, but the imagery suggests rejection. What stays with you is the speaker's honesty, since they knew the risk and gave their feelings anyway.