Many partnerships in life tend to break for several reasons. Firstly, the second law of thermodynamics must hold - that everything goes to entropy. That everything tends to degenerate and fall apart or disintegrate if no external energy is expended to keeping it happening so. The other reason is that we expect others to behave as we do and so when that does not happen, the relationship falters and if left unattended will fall apart. The other is the lack of awareness on the part of the partners of the nature of us individuals. When this awareness is gained or is imbued into us, then it would dawn on us of our idiosyncrasies and that these personality traits cannot be just wished away. This awareness, if instilled and such constructs when reflected upon deep enough and accepted as truths, we will think twice or even more before making our judgments on the other person. Being judgmental is perhaps the most salient weakness in us and that which needs to be guarded against if partners want to maintain a harmonious relationship. But no doubt, this is also the most difficult, for this is the ego in full action. We don't want to relinquish our viewpoints and opinions, for the ego’s stubbornness to hold on, for it would say to us that giving up means losing. So that view point becomes what we are, for no one wants to lose; it is the protection of our individuality, and so, it would seem that if our individuality is forfeited then we are lost. Modern life with its egoism, selfishness and individuality that is always looking for competition and the indulgence of greed for gain, is the reflection of bloated egos.
With that mindset, sublime values that lets go of attachments cannot happen and signals the destruction of relationships and partnerships. In the case of marriage which is an example of a partnership like no other in its sacredness to the upliftment of society, its breakdown is also about our inability to fathom individual differences and accept these as spiritual virtues. The breakdown indicates the rise of the ego and the conflict of personalities. The book "men are from mars and women are from venus" gives a good peek into this aspect of personalities that nature has bestowed on us to be what we are. It’s a great example of the difference between the mindset of men and women and a signal for learning to understand the genesis of our separate thought processes and being mindful of dialoguing to those sensibilities rather than to the selfish callings of the ego.
Like a marriage, our lives are full of partnerships, for relationships are what make us thrive as humans and more generally as living beings. Social harmony must be built on such a foundation of awareness - a move away from the selfishness and greed that manifests as the want for wealth, power, position and visibility, to that wonderful state of being that can make us feel that we belong to everybody. As a famous spiritual saying goes - "first we are nobody, then we are somebody, then we must strive to be everybody".