"Let us but see," said Iuchar and Iucharba to their brother Brian, "the land of Erin again, the hills round Telltown, and the dewy plain of Bregia and the quiet waters of the Boyne and our father's Dun thereby, and healing will come to us; or if death come, we can endure it after that." Then Brian raised them up; and they saw that they were now near by under Ben Edar; and at the strand of the Bull they came to land.

That is from the Mythological Cycle.
In the Heroic Cycle it appears in the longing cry for return to Ireland of Naisi and his brothers, which drives them out of Alba to their death; but otherwise it is rarely expressed.

In the Fenian Cycle it exists, not in any clear words, but in a general delight in the rivers, lakes, woods, valleys, plains, and mountains of Ireland.

Every description of them, and of life among them, is done with a loving, observant touch; and moreover, the veil of magic charm is thrown over all the land by the creation in it of the life and indwelling of the fairy host.

The Fianna loved their country well.
When Christianity came, this deep-set sentiment did not lessen.