The Roman Catholic Church encourages the faithful to make frequent, if not daily, communion. Today, the normal opportunity to receive the Eucharist comes at daily Mass. (In the past, many parishes, especially in cities, distributed the Eucharist before and after Mass for those who weren't able to attend the whole Mass.)
When we cannot make it to daily Mass, however, we can still make a spiritual communion, in which we express our faith in Christ and in His Presence in the Eucharist, and we ask Him to unite Himself with us. The following text is a popular form of spiritual communion; you can memorize it or use it as a guide to offering your own act of spiritual communion in your own words.
An Act of Spiritual Communion
My Jesus, I believe that You are present in the Most Holy Sacrament.
I love You above all things, and I desire to receive You into my soul.
Since I cannot at this moment receive You sacramentally, come at least spiritually into my heart. I embrace You as if You were already there and unite myself wholly to You. Never permit me to be separated from You. Amen.