St. Thérèse looked forward to Corpus Christi for many reasons, as she saw it as a beautiful feast that honored her greatest love in life, Jesus Christ, present in the Holy Eucharist.
In particular, she had fond memories of it as a child and wrote about it in her autobiography, Story of a Soul.
She mentions it first in connection to her retreat before receiving the sacrament of confirmation, which at that time was given at a younger age.
Ordinarily, there was only one day of retreat made for Confirmation, but the bishop was
unable to come on the appointed day and so I had the consolation of having two days of solitude. To distract us our mistress brought us to Mont Cassin and there I gathered very many big daisies for the feast of Corpus Christi. Ah! how happy my soul was!
It should come as no surprise that St. Thérèse loved flowers of all kinds, and many local traditions surrounding Corpus Christi involve flowers.
For example, it is often customary for girls to precede the Eucharistic procession, strewing flowers in front of the priest carrying the monstrance.
This is something that St. Thérèse loved most of all, as she explains in her autobiography.
The feasts! what memories this word brings back to me. How I loved the feasts! You knew how to explain all the mysteries hidden under each, and you did it so well that they were truly heavenly days for me. I loved above all the processions in honor of the Blessed Sacrament. What a joy it was for me to throw flowers beneath the feet of God! Before allowing them to fall to the ground, I threw them as high as I could and I was never so happy as when I saw my roses touch the sacred monstrance.
St. Thérèse had an innocent and childlike faith that persisted as she grew older.
She treasured these memories in the convent and looked forward to the times she spent in prayer before Jesus, her spouse, in the Blessed Sacrament.
