To be united in marriage, family, and church, we must be of one mind (Acts 4:32; Phil 2:2 in the Greek). We all instinctively realize this, so we try to change others' minds to make them like ours. This doesn't work. In fact, when we realize that someone is trying to change our minds, we often rebel and become even more disunited.
There is one way by which we can be of one mind. We can agree to change our minds and "have this mind" among ourselves "which was in Christ Jesus" (Phil 2:5, old RSV). If you and I are of one mind with Christ, we are of one mind with each other. We are united in Christ.
When we are of one mind with Christ and other Christians, we, like Christ, come to serve rather than to be served (Mt 20:28). We look "to others' interests rather than" our own (Phil 2:4). This deepens our unity with Christ and others. As we discover the depths of love in the mind of Christ, we become one as the Holy Trinity is one (see Jn 17:21).