Anyone who wishes to come after me, through me, to me. After me because I am Truth, through me because I am the way, to me because I am the life.
Any who wish to come after me, let them deny themselves and take up their cross and follow me. Christ, the power of God and the wisdom of God, messenger of great counsel, proposed three things to the rational soul made in the Trinity’s imaged: servitude, worthlessness, severity.
Servitude is indicated by denial of self, worthlessness by enduring of the cross, and severity by imitation of Christ. Thus a soul who has fallen from a state of triple happiness by disobedience may arise from a humiliated torment of triple misery by obedience. She had indeed fallen from herself, from the fellowship of angels, from the vision of God, that is, from freedom, from dignity, from blessedness.
Let her listen therefore to counsel so that by denying herself, that is, denying self-will, she may restore freedom of herself. By taking up her cross, that is, by crucifying her flesh with its vices and concupiscence, by the good of self- control, she restores her fellowship with angels: by following Christ, that is, by imitating his passion, she restores the vision of his clarity, because if we suffer with him, then we shall also reign with him.
Bernard of Clairvaux, Monastic Sermons, Sermo 63: Concerning Matthew 16:24 (CF 68. P. 281)