The short story of the feast is explained in my trusty old catechism:
A single word of Christ would have fully sufficed to redeem us, but it was not enough to make manifest the love of God. It is because of the great love Christ displays towards us, that we venerate the most Sacred Heart of Jesus. The heart is the centre of the physical life; from it the blood flows into every part of the body, maintaining its vitality. And since there is an intimate connection between body and soul, the heart is spoken of as the centre of the spiritual life, whence all the thoughts and feelings take their rise. Hence we say: “My heart rejoiced, my heart is grieved, etc.” The heart is regarded pre-eminently as the seat of love. When we venerate the Sacred Heart of Jesus, we call to mind His exceeding great love for us, and are stimulated to return love for love. God made use of a French nun at Paray-le-Monial, named Margaret Mary Alacoque, to propagate this devotion. Our Lord appeared to her repeatedly, showing her His Heart pierced by the lance, emitting flames of fire, surrounded by a crown of thorns to signify the pain sinners cause to Our Saviour and surmounted by a shining cross. Our Lord intimated His desire that pictures of this Heart should be exposed for veneration, and promised signal blessings to all who should practice this devotion. He also commanded the festival of the Sacred Heart to be kept on the Friday after the octave of Corpus Christi. This day is a most appropriate one, for it was on a Friday that Our Lord by His death gave the greatest possible proof of His love, and His Heart was pierced by the lance. Moreover the Adorable Sacrament of the Altar affords abundant testimony to the love of the Saviour, for as the sun’s rays are focussed in a lens, so the rays of the sun of divine love are concentrated in the Sacrament of the Altar. Hence the feast of Corpus Christi is a special memorial of the love of Christ for man. The devotion to the Sacred Heart, opposed at the outset, as are all works that are of God, spread rapidly over all the earth, and was attended by signal blessings. Another reason why Our Lord suffered so much was that He might be a pattern to us in suffering: “Christ suffered for us, leaving you an example” (1 Pet. ii. 21). He Himself said: “I have given you an example” (John xiii. 15).
Did you catch that part above: He promised signal graces to those who would venerate His Sacred Heart today. Even if it is the moving of your heart to thank Our Lord for loving you so much, do it today.
Photo by Lawrence OP 
This article, Do Something to Honor the Sacred Heart of Jesus Today on the Feast is a post from The Bellarmine Forum.
https://bellarmineforum.org/do-something-to-honor-the-sacred-heart-of-jesus-today-on-the-feast/
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