This is an extension of Hegel's interpretation of the Unity of Opposites.

"The principles of the metaphysical philosophy gave rise to the belief that, when cognition lapsed into contradictions, it was a mere accidental aberration, due to some subjective mistake in argument and inference. According to Kant, however, thought has a natural tendency to issue in contradictions or antinomies, whenever it seeks to apprehend the infinite. We have in the latter part of the above paragraph referred to the philosophical importance of the antinomies of reason, and shown how the recognition of their existence helped largely to get rid of the rigid dogmatism of the metaphysic of understanding, and to direct attention to the Dialectical movement of thought. But here too Kant, as we must add, never got beyond the negative result that the thing-in-itself is unknowable, and never penetrated to the discovery of what the antinomies really and positively mean. That true and positive meaning of the antinomies is this: that every actual thing involves a coexistence of opposed elements. Consequently to know, or, in other words, to comprehend an object is equivalent to being conscious of it as a concrete unity of opposed determinations. The old metaphysic, as we have already seen, when it studied the objects of which it sought a metaphysical knowledge, went to work by applying categories abstractly and to the exclusion of their opposites."

To know something you know what it is not, as knowning what something is in itself is impossible. There cannot be heat without cold, just as there cannot be nothingness without somethingness.

There cannot be reason without emotion or love without hate.

To experience either form of the an opposite is to better know both of them. Whether an experience is good or bad is to an extent irrelevant as that experience has led you closer to knowing the good.