According to Osho, when understanding is absent, even decades together leave lovers as strangers. The mind's flux projects shifting images: honeymoon one moment, a China Wall the next, so you meet your idea, not the person. Without self-knowing and awareness of the silent 'screen' behind mind, relationship stays superficial, unstable, and dreamlike.
Without real understanding, you live with your own picture of your partner, so closeness comes and goes and they feel like a stranger.