When assessing the potential for growth and compatibility of a couple I consider the level of trust and commitment that exists between them. If one of them is not committed to the relationship it has little chance of success. If there is limited trust between partners it is going to be difficult for the relationship to grow while working through the conflicts that are always present.
Normal relationships begin with levels of trust that is limited and it develops as the relationship evolves. A healthy person has a normal suspicion of others. If one of the partners has never been able to trust others growth is going to be a challenge. Those with attachment issues is going to be particularly cautious about trusting others. Being in conflict with a partner can trigger past memories and emotional upsets presenting vulnerabilities that people respond to in many ways. Being able to trust a partner in conflict provides the opportunity for individuals to know that their inner weaknesses will not be used against them. Being in conflict provides a window for resolution or compromise, which provides for long term growth.