The speaker begins with a strange kind of certainty: they are "confirmed in loss." Where we might expect confirmation to mean something hopeful, as in a religious ritual or a settled belief, here it means being sure of sorrow. The phoenix usually stands for rebirth, the bird that rises from its own ashes. Bonta turns that idea around. The speaker is a phoenix, but the cycle that matters is the falling, not the rising.
The last lines make this sharper. The speaker is "resolving by the grace of God to fall hard again." Grace is normally something that lifts us up, yet here it seems to grant the strength to fail once more. The tone is dry, almost darkly humorous, and also tired. There is resignation in it, but also a stubborn kind of courage: the speaker accepts that loss will keep returning and chooses to meet it anyway. The mood is quiet, bleak and oddly defiant.