The way you wrote this is so simple, but in its simplicity, I believe you hold a voice that reveals the truth of depression or where you find yourself now. Stuck No dramatization, no big details, just the raw truth.
I liked how you played on "down", as that can be a direction for some, or a state of mind for others. How far down can the heart go? How far can our hopes and dreams fall? The simile showed that yearning for a light, drawn to something that will give hope, as your last two statements show you have tried - yet are close to giving up. Don't give up, keep the fight!
And welcome to PnQ by the way, hope you continue to share your voice and feel free to read others' poetry or join in on discussions.