“Since human love can so easily become tainted with selfishness and sensuality . . . it is necessary that one maintain a strict vigilance lest one’s love should exceed the limits of virtue and become an occasion of evil. For if it is true that a good friend is a powerful stimulus to virtue, it is no less true that one of the most destructive forces in the Christian life is that of a sinful friendship. . . . it happens frequently that a human friendship begins in a virtuous manner but imperceptibly but surely becomes mixed with sensual love and finally terminates in carnal love.
For this reason it is extremely important that one know the signs by which one can determine whether a friendship is sensual. The first and most evident sign of a sensual friendship is that it is exclusive. This exclusiveness is shown by the fact that the two friends withdraw from the company of others in order to be alone, are annoyed if others join their company, and are jealous of each other to the point of becoming angry if one sees the other in the company of a third party. Secondly, a sensual friendship is characterized by possessiveness, which may reach such a point that one cannot tolerate the absence of the other, seeks to prolong conversations and visits unduly, and dominates the other person. Thirdly, sensual friendships are obsessive. At the slightest provocation one’s thoughts turn to the friend; on entering a room the first person sought is the friend; the imagination seems always to be focused on the face of the friend, and this to the point of distraction in prayer or in the performance of one’s duties.
In order to avoid this type of friendship, which is harmful to the spiritual life, the best remedy is to prevent such a friendship from developing. As soon as any of the signs have been noticed, one should react as to the symptoms of a disease. If, however, such a friendship has already been allowed to develop, it may be necessary to avoid any drastic and sudden measures but rather to let the friendship gradually cool until it can be rectified. Spiritual directors and confessors, who are prone to react violently to such friendships and to demand of their penitents an immediate and definitive break between the friends, may unwittingly cause a psychological upheaval more serious than the disorder they hoped to cure.”
Jordan Aumann, Spiritual Theology, 379-80.