I lowkey hate when life starts feeling like this song

Or this

Or this

My mistake was making you a priority when I was your second choice.

I tried looking up the song meaning thinking it was about Ireland too, but I found none so I'll just talk about it from my own perspective.

This song reminds me of a toxic, cyclical relationship with themes of betrayal, manipulation, and obsession. The lyrics describe a person who is drawn to someone they know is terrible for them, using imagery of a dangerous, yet alluring, they are drawn to each other one way or another.

The writer from is talking to a terrible person, whether terrible for him to be with or in general

(" can't find a good word for you")

It also seems like the writer that's talking about Jackie can't seem to get away from them and utterly obsessed with them but still knowing at the same time the other person is terrible for them and makes a terrible cycle (maybe that's why the song is repetitive).
Sally in this song may be the person who introduced the two of them together.

(This is not official just my POV)

"Something happens in the morning, when I can't see those failing eyes.
I can't find a good word for you, does it come as a surprise?"

"I don't think we'd rhyme.
I will wear you down in time.
I will hurt you, I'll desert you.
I am Jackie down the line."

"I don't think we'd rhyme.
I will make your secrets mine.
I will hate you, I'll debase you.
I am Jackie down the line."

"What good is happiness to me if I've to wield it carefully?
For care I'll always come up short, It's only right;
I don't think we'd rhyme."

"I don't think we'd rhyme.
I will wear you down in time.
I will hurt you, I'll desert you.
I'm one Jackeen of a line.

I don't think we'd rhyme.
I will take up all your time.
I will chew you, I'll go through you.
I am Jackie down the line.

I don't think we'd rhyme.
I will make your secrets mine.
I will hate you, I'll debase you.
I am Jackie down the line.
And I will stone you, I'll alone you.
I am Jackie down the line.
If I can make you, I can break you.
I am Jackie down the line.
I am Jackie down the line."

"Countless times I trusted you, I let you back in, Knowing, learning, you know I should have run, but I stayed.
Maybe I always knew my fragile dreams would be broken for you.

Today I introduced myself to my own feelings in silent agony, after all these years, they spoke to me after all these years."