Value your parabatai," he said. "For it is a precious bond. All love is precious. It is why we do what we do. Why do we fight demons? Why are they not fit custodians of this world? What makes us better? It is because they do not build, but destroy. They do not love, but hate only. We are human and fallible, we Shadowhunters. But if we did not have the capability to love, we could not guard humans; we must love to guard them. My parabatai, he loved like few ever could love, with all and everything. I see you are like that too; it burns more brightly in you than the fire of Heaven

It was at the outskirts of the world that the Old Things accumulated, like driftwood round the edges of the sea. ("The Troll")

The degree of freedom we enjoy outwardly is a reflection of the degree of love we cultivate inwardly.

Force is incomplete and therefore has to be fed energy constantly. Power is total and complete in itself and requires nothing from outside.

After all, it isn't the facts of one's environment, but one's attitude toward them, that determines whether one will be defeated or victorious.

Perceptual fields are limited by the attractor patterns that they're associated with. This means that the capacity to recognize significant factors in a given situation is limited by the context that arises from the level of consciousness of the observer. The motive of the viewer automatically determines what is seen; causality is, therefore, ascribed to factors that are, in fact, a function of the biases of the observer and aren't at all instrumental in the situation itself.