This etymology matters. Repair is not the same as return. The couples who survive significant rupture are not the couples who manage to go back to some prior version of their relationship. That version, by definition, no longer exists — and if it did, it would be the version in which the rupture was also already forming, silently, in the conditions that made it possible. Repair is always forward-facing. It is the building of a relationship that can accommodate what has been revealed, a relationship that includes the knowledge of the break.
What makes repair difficult is not usually the willingness to forgive. It is the willingness to understand. Forgiveness without understanding is, at best, a form of generosity and, at worst, a mechanism for bypassing what needs to be looked at. The things that lead to betrayal, to withdrawal, to the slow accumulations of resentment that end with someone sleeping in a separate room — these things did not appear from nowhere. They were built, usually slowly, by both people, in conditions that both helped create.
Repair, in the psychoanalytic sense, is always also self-repair. It requires each person to look at what they were defending against, what they were not saying, what conditions they were creating or tolerating. This is not to equalise blame where it is not equal. It is to recognise that relationships are co-created systems, and that rupture, however it finally manifests, usually has a longer prehistory than the moment of its crisis.