"Man is a being who bears within his heart a thirst for the infinite, a thirst for truth – a truth which is not partial but capable of explaining life’s meaning – since he was created in the image and likeness of God. The grateful recognition that life is an inestimable gift, then, leads to the discovery of one’s own profound dignity and the inviolability of every single person.... Only in relation to God does man come to understand also the meaning of human freedom. It is the task of education to form people in authentic freedom. This is not the absence of constraint or the supremacy of free will, it is not the absolutism of the self. When man believes himself to be absolute, to depend on nothing and no one, to be able to do anything he wants, he ends up contradicting the truth of his own being and forfeiting his freedom. On the contrary, man is a relational being, who lives in relationship with others and especially with God. Authentic freedom can never be attained independently of God."
The Message also contains a link to another text from 2005 where Pope Benedict summarizes the "theology of the body" and of the family. Both are worth reading in full.