St. Valentine was a holy priest in Rome who brought help and comfort to the martyrs during the persecution. To abolish the heathen custom of boys drawing girls’ names in honor of their goddess Februata Juno, several zealous pastors substituted the names of saints in billets given on this day.
Grant, we beseech Thee, O Almighty God, that we who keep the birthday of the blessed martyr Valentine may be delivered by his prayers from all the ills that hang over us. — Collect
The Imitation of Christ
Write, read, sing, lament, keep silence, pray, bear adversities manfully: eternal life is worth all these, and great combats.
So much disagreeable nonsense has been attached to the observance of this day that St. Valentine cannot be honored by some of it. However, if you can make someone happy or even make them laugh heartily over a valentine today, that is not out of place entirely. Be very careful, though, that there be no possibility of offense.
We send a valentine to those we love. You'll not forget today, then, to send a little valentine by way of an ejaculation or an act of mortification to our Lord and another to His Mother and a little plain one to St. Joseph and a rather elaborate one to your Guardian Angel. They will probably tell each other about getting them from you but they'll not be jealous.
I love them that love me. (And the saints do.)