Pope John Paul II wrote about 'spiritual commnunion' in Ecclesia de Eucharistia
"Unlike any other sacrament, the mystery [of the Eucharist] is so perfect that it brings us to the heights of every good thing: Here is the ultimate goal of every human desire, because here we attain God and God joins himself to us in the most perfect union."
Saints who were deeply immersed in the spiritual life tell us to pray for a constant desire for the Sacrament of the Eucharist. The practice of 'spiritual communion' naturally flows from this desire.
The Church affirms its importance for daily spiritual growth.
"When you do not receive communion and you do not attend Mass, you can make a spiritual communion, which is a most beneficial practice; by it the love of God will be greatly impressed on you."
[St. Teresa of Avila, The Way of Perfection, Chapter 35]