This is the Anima Christi, as freely translated in verse by John Henry Cardinal Newman. I find it very comforting to say as my last prayer while lying in bed waiting for sleep.
(My usual bedtime is 2:00 am, old student habit, I think; and usually by 2:00 I'm in such a trance of fatigue I can scarcely get up from my knees from my usual night prayers. But when I get fatigued my mind wanders all over the place; many times it wanders to wondering how wonderful it would be to have a warm soft cuddly wife in bed with me. And since this is a thought I must not think, for obvious reasons, I say the Anima Christi. If I'm not asleep by then, I start saying the Stations of the Cross, and rarely get to the end.)
So here it is:
Soul of Christ, be my sanctification.
Body of Christ, be my salvation.
Blood of Christ, fill all my veins.
Water of Christ's side, wash out my stains.
Passion of Christ, my comfort be.
O good Jesus, listen to me.
In Thy wounds I fain would hide,
Ne'er to be parted from Thy side.
Guard me should the Foe assail me,
Call me when my life shall fail me,
Bid me come to Thee above,
With Thy saints to sing Thy love
Forever and ever. Amen.
The Latin is elegantly sparse and compact; a literal translation equally so; I like this best.