For me, God’s revelation of self as three Persons is an invitation to every kind of relationship with God we could ever desire in the course of our lifetime. When we are younger, we need to relate to God from our perspective of loving, obedient child, so God is there for us as Father. As we grow, we become disciples, seeking the friend, brother and Master we find in Jesus. Maturing in the spiritual life, we are invited into greater intimacy and sharing of the Life and Gifts of God through relationship with the Holy Spirit. We can enjoy relating to any or all three Persons of the Trinity at any time depending on our spiritual needs and desires at that moment in our life.
The Russian icon by Rublev is one of my favorites, depicting three persons (angels) at a Eucharistic table with a small opening in the front for us to enter into if we wish. Mary took her place at that table as Daughter of the Father, Mother of the Son, and Spouse of the Holy Spirit. She leads the way and invites us by example to join her at this Feast of Divine Love. Happy Trinity Sunday!