Unity can be quite difficult to achieve and even then when there is apparent unity, it can also be fragile.
There are two factors that unity can stand upon, and that is a common love and/or a common enemy.
But if there is no common love and worse still, if the enemy is within, then it can be certain that there will be serious division.
Jesus even said in the gospel that if Satan is divided, his kingdom cannot stand at all.
And if the Church is divided, then similarly, the Church cannot stand at all.
In the 1st reading, the prophet Joel urged the people to be united in prayer and penance to invoke God's protection against an impending disaster.
We too need to be united in love and in prayer to the Sacred Heart of Jesus.
And united as Church in love and prayer and with God's blessings, we will be able to stand up to any danger or enemy.