Mbo - do I get you right, and you think "The Boys of Barr Na Sraide" is a cheery song?
But I'm with you on preferring sad songs to most happy songs when I want to lift myself, and "The Boys of Barr Na Sraide" might be one of them. You can't beat death in a song.
There's a time for happy songs, but not when you're sad. And not really when you're at your most happy either.
I think G.K.Chesterton got it essentially right, about the songs anyway, when he wrote:
"For the great Gaels of Ireland
Are the men that God made mad,
For all their wars are merry,
And all their songs are sad."
That's from The Ballad of the White Horse - and if you want to read the rest of it, click on the title. (To find the quote, write Gaels in the Find facility of your browser, and click a couple of times, till it comes up.)