Max

“A human being is spirit. But what is spirit? Spirit is the self. But what is the self? The self is a relation that relates itself to itself or is the relation's relating itself to itself in the relation; the self is not the relation but is the relation's relating itself to itself. A human being is a synthesis of the infinite and the finite, of the temporal and the eternal, of freedom and necessity, in short, a synthesis. A synthesis is a relation between two. Considered in this way a human being is still not a self.... In the relation between two, the relation is the third as a negative unity, and the two relate to the relation and in the relation to the relation; thus under the qualification of the psychical the relation between the psychical and the physical is a relation. If, however, the relation relates itself to itself, this relation is the positive third, and this is the self.”
― Søren Kierkegaard, The Sickness Unto Death: A Christian Psychological Exposition for Upbuilding and Awakening

“That human life must be some kind of mistake is sufficiently proved by the simple observation that man is a compound of needs which are hard to satisfy; that their satisfaction achieves nothing but a painless condition in which he is only given over to boredom; and that boredom is a direct proof that existence is in itself valueless, for boredom is nothing other than the sensation of the emptiness of existence.”
― Arthur Schopenhauer, Essays and Aphorisms

“if adversity and hopeless grief have quite taken away the taste for life; if an unfortunate man, strong of soul and more indignant about his fate than despondent or dejected, wishes for death and yet preserves his life without loving it, not from inclination or fear but from duty, then his maxim has moral content.”
― Immanuel Kant, Groundwork of the Metaphysics of Morals

“Now it is clear, God cares only for what is his, busies himself only with himself, thinks only of himself, and has only himself before his eyes; woe to all that is not well pleasing to him. He serves no higher person, and satisfies only himself. His cause is - a purely egoistic cause.”
― Max Stirner, The Ego and Its Own and The False Principle of Our Education