It’s good to watch our own speech; it’s good to listen and learn from others; it’s good to undertake fresh study into the Christian faith itself. But the Christian faith, though asking the best of our minds, is never content with only our minds. “You shall love the Lord your God with all your heart and with all your soul and with all your mind and with all your strength” (Mark 12:30).
And so Unitatis Redintegratio says:
“There can be no ecumenism worthy of the name without a change of heart. For it is from renewal of the inner life of our minds, from self-denial and an unstinted love that desires of unity take their rise and develop in a mature way. We should therefore pray to the Holy Spirit for the grace to be genuinely self-denying, humble. gentle in the service of others, and to have an attitude of brotherly generosity towards them.
“This change of heart and holiness of life, along with public and private prayer for the unity of Christians, should be regarded as the soul of the whole ecumenical movement, and merits the name, ‘spiritual ecumenism.’” (§§7–8)
For more on this—in fact, if you want to jump right in and see this happen in your own community—you could do no better than take a look at A Handbook of Spiritual Ecumenism by Cardinal Walter Kasper, retired just this year from the Pontifical Council for Promoting Christian Unity. Another very accessible, hand-on, and fun-to-read approach is found in a book by ecumenical Baptist Steven R. Harmon, Ecumenism Means You, Too: Ordinary Christians and the Quest for Christian Unity.