Humans can be compared to trees. When a tree encounters a physical obstacle to its expansion, especially its roots, its branches, they curl around it. They kind of circumvent it. They formed maybe, ugly maybe, but they reach the destination, however late, however partially.
Psychopathologies are the same. They are actually adaptive mechanisms. They allow the individual to continue to grow around obstacles.
The nascent personality twists and turns, deforms itself, is transformed until it reaches a functional equilibrium at homeostasis, which is not too egodystonic, not too unpleasant, unacceptable to the individual.
And having reached this point, everything settles down. Everything settles down and continues its more or less linear pattern of growth.
The forces of life as expressed in the development of the personality are stronger than any hindrance, any obstacle, any stress, any challenge.
The roots of trees, remember, they crack mighty rocks and pavements. Microbes live in the most poisonous surroundings, extremophiles.
Similarly, humans are a life form and humans form these personality structures, which are optimally suited to their needs and to the outside constraints.
Such personality configurations may be abnormal, but they're mere existence proofs that they had triumphed in the delicate task of successful adaptation.
In other words, one thing you can say in favor of narcissists and psychopaths and borderlines, they're alive. They're alive. They're not dead. They're survivors.
Only death puts a stop to personal growth and development. Life's events, crises, joys and sadness, disappointments, surprises, setbacks, successes, all these contribute to the weaving of the delicate fabric that we call personality.