… he who is guided by the Spirit does not always remain in the same state. He does not always advance with the same facility. “The course of man is not in his control.” It rather depends on the guidance of the Spirit who sets the pace as he pleases, sometimes torpidly, sometimes blithely, teaching him to forget the past and to strain ahead for what is still to come. …
Therefore when you feel weighed down by apathy, lukewarmness and fatigue, do not yield to cowardice or cease to study spiritual truths, but look for the hand of the one who can help you, begging like the bride, to be drawn, until finally, under the influence of grace, you feel again the vigorous pulse of life. Then you will run and shout out: “I run the way of your commandments since you have enlarged my heart.” But while this state of happiness remains, you must not use it as if you possessed God’s gift by right of inheritance, secure in the conviction that you could never lose it; for if he should suddenly withdraw his hand and withhold his gift, you would be plunged into dejection and excessive unhappiness. When you feel happy beware of boasting: “Nothing can ever shake me!” For you may be compelled to repeat for yourself the Psalmist’s sad comment: “But when you hid your face and I was terrified.” If you are wise you will try to follow the advice of the Wise Man: in the time of adversity not to be unmindful of prosperity, and in the time of prosperity not to be forgetful of adversity.
Bernard of Clairvaux On the Song of Songs II, Sermon 21 “The Love of the Bride, the Church, for Christ” v, 4,5 (CF 7, p. 7-8)