The mystery of the Holy Trinity is the central mystery of faith and Christian life.
The mystery of the Holy Trinity is the central mystery of Christian life and faith. It is the mystery of God in himself. It is therefore the source of all the other mysteries of faith, the light that enlightens them. It is the most fundamental and essential teaching in the « hierarchy of the truths of faith" (DCG 43). The whole history of salvation is identical with the history of the way and the means by which the one true God, Father, Son, and Holy Spirit, reveals himself to men » and reconciles and unites with himself those who turn way from sin" (DCG 47).
(CCC, 234)
This is what the liturgy recalls by celebrating the Solemnity of the Holy Trinity.
Mary is closely associated to the mystery of the Holy Trinity
The Virgin Mary (…) receives this immense mission and the dignity to become the Mother of God, therefore the daughter of predilection of the Father, and the sanctuary of the Holy Spirit, a gift of an extraordinary grace which places her far above all the creatures in heaven and on earth.
(Vatican II, Lumen gentium).
Thus all Marian spirituality, as Saint Louis Grignion de Montfort taught by example, derives from the Trinity and leads to Mary.