The speaker is writing about a moment when they nearly ended their life, and about what pulled them back. The opening question, "what are you living for?", is one they've heard too often, and they admit they had no real answer to it. Four months ago, they say, they might have answered very differently.
Then comes the turning point. Just as they were "ready to jump," they heard a voice, "the most beautiful noise" they had ever heard. We're never told whose it is, only that it's "her" voice, and that it made everything suddenly clear. The plain, unadorned lines make the shift feel sudden and real.
The mood moves from heavy and weary to quietly hopeful. The final line, "it's all uphill from here," is a little ambiguous: uphill suggests effort and a hard climb, yet the speaker says it with relief, as though having a direction at all is the victory.