The 23-year-old man, who has pleaded guilty to killing his partner Sara Staunton, in Mayo Abbey in December 2013, is to be sentenced next month.
In a letter read to the Central Criminal Court in Dublin on Monday, Ray Gralton, said the tragic events surrounding Ms Staunton’s death will haunt him for the rest of his life.
He pleaded guilty to manslaughter.
The Central Criminal Court heard Gralton and Ms Staunton (28 ) had been in a turbulent relationship for about a year prior to her death.
They argued on December 13. Gralton, a trained boxer, punched Ms Staunton a number of times.
Themother-of-two went to bed and Gralton was unable to wake her.
She died of blunt force trauma to the head.