The speaker is walking away from someone they still love, and the poem is the sound of that decision being made. It opens with a nervous question, asking whether the other person feels "lighter" now that the speaker is gone. That hints at hurt and a little doubt about whether they were ever a burden.
The central image is water slipping through fingers: the harder the speaker grasps, the more the person escapes. The colors work the same way. Yellow suggests warmth and sunlight, while a black "darker than the skies at 3 a.m." suggests low, lonely moods. The speaker says they want to love every shade, but they can't keep holding on.
The reason comes near the end. They loved this person more than themselves, and it is tearing them apart. The last lines are bleak, since the love they are "gaining back" for themselves goes "into nothing." The mood is tired, honest, and sad, with grief mixed in with a fragile attempt at self-protection.