This beautiful poem was originally written by a Christian abbot, but it translates well into a Pagan or Wiccan context. In the early 20th century, Kuno Meyer edited and translated it in Miscellanea Hibernica and credited it to a monk named Fer Fio mac Fabri. Its original name has been lost to the centuries, but it's still as lovely today as it was when it was first written, somewhere in an Irish monastary. You can incorporate it into a ritual or ceremony, or use it as a focused meditative prayer.
I invoke the seven daughters of the sea
who fashion the threads of the sons of long life.
May three deaths be taken from me,
May three periods of age be granted to me,
May seven waves of good fortune be dealt to me,
May no evil spirits harm me on my journey,
In flashing breastplate without hindrance,
May my fame not perish and my name not pledge in vain,
May death not come to me until I am old!
I invoke the silver champion of the seven periods of time,
Whom fairy women have reared on the breasts of plenty.
May my seven candles not be extinguished.
I am an indestructable stronghold.
I am an unshakable rock.
I am a precious stone.
I am the luck of the week.
May I live a hundred times a hundred years,
Each hundred of them apart,
as I summon their boons to me.
May the grace of the Divine be upon me!