Sometimes people begin, discover how much pain and fear they are holding, and adaptively decide to take whatever gains they have made and stop. Occasionally we reach the limits of our competence or capacity and must help one of people find someone or a nest of people who can hold their wounds when we can't. We could likely add other situations in which we have parted with someone early in the relationship or at a time that seemed premature. All of this is part of human limitation in both of us.
Bonnie Badenoch The Heart of Trauma: Healing the Embodied Brain in the Context of Relationships