Christian, learn from Christ how you ought to love Christ. Learn a love that is tender, wise, strong; love with tenderness, not with passion, wisdom, not foolishness, and strength, lest you become weary and turn away from the love of the Lord. Do not let the glory of the world or the pleasure of the flesh lead you astray; the wisdom of Christ should become sweeter to you than these. The light of Christ should shine so much for you that the spirit of lies and deceit will not seduce you. Finally, Christ as the strength of God should support you so that you may not be worn down by difficulties. Let love enkindle your zeal, let knowledge inform it, let constancy strengthen it. Keep it fervent, discreet, courageous. See it is not tepid, or temerarious, or timid. … So love the Lord your God with the full and deep affection of your heart, love him with your mind wholly awake and discreet, love him with all your strength, so much so that you would not even fear to die for love of him. … [K]eep him as a strong light for your mind and a guide for your intellect, not only to avoid the deceits of heresy and to preserve the purity of your faith from their seductions, but also that you might carefully avoid an indiscreet and excessive vehemence in your conversation. Let your love be strong and constant, neither yielding to fear nor cowering at hard work. Let us love affectionately, discreetly, intensely. We know that the love of the heart, which we have said is affectionate, is sweet indeed, but liable to be led astray if it lacks the love of the soul. And the love of the soul is wise indeed, but fragile without the love which is called the love of strength.
Bernard of Clairvaux, On the Song Of Songs I, Sermon 20 “Three Qualities of Love,” v. 4 (CF 4, p. 149f)