The first half of the sentence means that this relationship has entered a dead end, and it will be nothing in the future, which is destined to be a bitter relationship; A, B, C and D in the second half of the sentence refer to strangers and symbolize strangers. It's better to be a stranger than to be entangled. It's a bit like "jack shall have Jill" in it. Expressed a kind of thoughts and feelings with too many experiences and gradually indifferent mentality, from which there seems to be a trace of regret and helplessness. Although unforgettable, but still want to forget each other, and finally chose to let go. There is a similar saying: if you dare not love or hate, it is better to be a party, a party, and a party. If you dare not love me or hate me, be a stranger. If a relationship can't see the future and feel the present, then it's better to clear the field as early as possible and be Party A and Party B ... After all, there are many different feelings in this world, but few of them agree.