The Catechism of the Catholic Church teaches us that "The mystery of the Most Holy Trinity is the central mystery of the Christian faith and of Christian life" (CCC 234).
This is because we are created in the image and likeness of God, as Scripture tells us.
Therefore, if God's essential nature is love, so is ours!
We have a built in openness to other people. We are incomplete by ourselves.
We are created to give ourselves to others and to receive others.
The Father, from all Eternity, loves the Son and pours himself into the Son, and the Son loves the Father in return.
And that mutual love is so complete that the Holy Spirit proceeds from it. Every human family is an image of this Trinitarian love.
This mysterious and wonderful doctrine about God, that he is both unity and trinity, is called by the Catechism "the central mystery of Christian faith and life" (CCC).
It is the center of our faith, because it gives us a glimpse into the inner life of God himself, the God we believe in.
And it's the center of our life, because we are called to be living images of God, created to love and be loved.
Jesus gave his Church the great commandment to "love one another as I have loved you."
He did not command us to make millions of dollars.
He did not command us to win awards and prizes.
He did not command us to be comfortable.
He commanded us to be like him: to love God with all our heart and to love our neighbor as ourselves.
And loving God leads automatically to loving our neighbor.
Pope Benedict wrote in his first encyclical: "In the saints one thing becomes clear: those who draw near to God do not withdraw from men, but rather become truly close to them" (Deus Caritas Est, 42).