And so what he's doing is providing a balance to the almost flippant attitude of the Pharisees to the marriage bond. And as always we need to let Scripture interpret Scripture. Similarly in 1 Cor 7 Paul says that if an unbeliever leaves his or her spouse, the spouse is no longer bound to that person. So there are cases where divorce and remarriage are allowed, because of people's hardness of heart. So marriage is good.
Marriage is permanent.
But sadly, the church isn't made up of impeccable saints. All of us are fallen creatures, all of us are sinful and hard of heart. All of us depend for our salvation on God's grace and forgiveness. And that's equally true in the area of marriage. Where our hardness of heart has affected our marriage, whether that effect has been terminal or simply hurtful, we need to turn to God in repentance and ask for his forgiveness.