They leave in the wrong order.
The big one you brace for goes first, sometimes, and then you are floored six months later in a supermarket by a jar of the mustard they liked. Nobody plans for the mustard.
Feelings don't queue and they don't finish in sequence. Something can be ninety per cent gone and still take an afternoon off you when a particular song comes on in a shop.
That is not a relapse and it is not lost ground. It is what leaving looks like from the inside — uneven, badly timed, and going anyway.