"Those who propagate this devotion shall have their name written in my heart, and it shall never be effaced."
Just as the priest devoted to the Sacred Heart will be rewarded with pastoral success, anyone in general - priest, religious or layperson - who promotes this devotion shall have the best of all rewards; to be engraved into the very Heart of Jesus, never to be erased. You become a permanent fixture in the Heart of Jesus.
All of us want to be included in that list of all lists, the Book of Life wherein the names of those going to heaven are recorded. That Book is the Heart of Jesus. We are all saved by Him, by the Sacred Blood He poured out for us, because His Heart loved us. When we accept that salvation and return His love, our names are engraved on His Heart and are written in the Book of Life.
But true promoters of this devotion are not simply those who encourage others to love the Sacred Heart by their words alone. We do more to turn people away from the faith when we do the opposite of our holy words. True promoters live what they preach. They strive for perfection, and as they do so, they do it with utmost humility, always accusing themselves of their faults and failings and always in the state of repentance, striving to be better each day with the grace of God through prayer and the sacraments.