Well yes, all relationships do end if you look at the matter from a ‘nothing is separate from anything else’ perspective. However the fact of and the living through the end of a relationship, be it through death or incompatibility or all the reasons people end relationships, the non dual seeing doesn’t take the pain away. Even though I find Rilke hard to follow I get what he is saying. And I think most of us can wish for a split that has some life and goodwill left after the explosion of separation. I remember the pain as more like an internal explosion which lasts some time. Disturbing.

Rilke on how to break up with integrity and preserve friendship after romance.
As soon as two people have resolved to give up their togetherness, the resulting pain with its heaviness or particularity is already so completely part of the life of each individual that the other has to sternly deny himself to become sentimental and feel pity. The beginning of the agreed-upon separation is marked precisely by this pain, and its first challenge will be that this pain already belongs separately to each of the two individuals. This pain is an essential condition of what the now solitary and most lonely individual will have to create in the future out of his reclaimed life.

He considers the measure of a “good breakup” — a separation that, however painful in its immediate loss, is a long-term gain for both partners, individually and together:

If two people managed not to get stuck in hatred during their honest struggles with each other, that is, in the edges of their passion that became ragged and sharp when it cooled and set, if they could stay fluid, active, flexible, and changeable in all of their interactions and relations, and, in a word, if a mutually human and friendly consideration remained available to them, then their decision to separate cannot easily conjure disaster and terror.