Faithfulness is not related to how we or other people feel. Faithfulness has nothing to do with circumstances. Faithfulness is not affected by the unfaithfulness of others. This is all true because faithfulness is an expression of character. And character doesn't go by feeling or circumstance or influence.
Faithfulness is the choice to do right because our character demands it.
They chose faithfulness. Despite Gomer's repeated and deliberate unfaithfulness, Hosea chose faithfulness. That faithfulness showed itself in mercy, love, forgiveness and restoration. Because of his faithfulness he could put up with far more than any husband should have to put up with. His character moved him to put her well-being and God's message ahead of himself.