From Pope St. John Paul II’s Apostolic Exhortation Familiaris Consortio (1981):
Various reasons can unfortunately lead to the often irreparable breakdown of valid marriages. These include mutual lack of understanding and the inability to enter into interpersonal relationships. Obviously, separation must be considered as a last resort, after all other reasonable attempts at reconciliation have proved vain.
Loneliness and other difficulties are often the lot of separated spouses, especially when they are the innocent parties. The ecclesial community must support such people more than ever. It must give them much respect, solidarity, understanding and practical help, so that they can preserve their fidelity even in their difficult situation; and it must help them to cultivate the need to forgive which is inherent in Christian love, and to be ready perhaps to return to their former married life.
The situation is similar for people who have undergone divorce, but, being well aware that the valid marriage bond is indissoluble, refrain from becoming involved in a new union and devote themselves solely to carrying out their family duties and the responsibilities of Christian life. In such cases their example of fidelity and Christian consistency takes on particular value as a witness before the world and the Church. Here it is even more necessary for the Church to offer continual love and assistance, without there being any obstacle to admission to the sacraments.
— Familiaris Consortio 83