I like the potential this carries. It's interesting that even after reading it through three times, I am unsure how the speaker truly feels about this departure. In most cases, this could be an issue with the poem not containing enough feeling, but it's different here.
It feels to me like when you've been in a relationship a long time and are left with no illusions. That last bit of a failed relationship really can feel like walking along an edge, knowing its fate but not wanting to admit it. This can take a couple around some weird and awkward contours, especially if both are being kind, but have simply found themselves incompatible. There is no stormy end, no abrupt change, just a slow growing apart, so that when one leaves it is not heartbreaking, but disorienting; maybe a poignant blend of wistfulness and relief.