On the face of it, winning an Oscar for best original song, and being feted by both Hollywood and the global music industry, must have been like a dream come true for Glen Hansard. But when he looks back at that night in LA's Kodak Theatre in March 2008 and on the subsequent couple of years, any pleasure he feels is tinged with sadness.
"That was a very intense time," the Dubliner says. "Suddenly, both me and Mar [his songwriting and romantic partner, Marketa Irglova] were in demand everywhere.
"After all those years trying to make it, we just didn't want to give up all the opportunities that were now coming our way. While that was great for our careers, obviously, it did play havoc with our relationship and, I suppose, brought it to a conclusion."
Last year's Rhythm and Repose – his debut solo album – alludes to such an emotional rollercoaster and, in a lengthy conversation before he soundchecks at a gig in Belgium, one senses the pain hasn't gone away.
"Nobody can ever look back on their lives and know for certain what would have happened if things had been different. I don't know if me and Mar would still be together if Once hadn't happened or if there had been no Oscar. Maybe we would, maybe we wouldn't."
The pair see very little of each other nowadays. "She lives in Iceland," he says. "We have gone down very different roads, she and I. The signs were there on Strict Joy [the second album they released under the Swell Season moniker]. It wasn't so much a collaborative effort, more two people writing songs separately.
"I don't know if we will make an album again. Probably not, to be honest. True collaboration is a very intimate experience and I don't know if we can do that now. Maybe we'll play live together one day."
Once truly changed the game for Glen Hansard. John Carney's sweet film – which was loosely based on the early days of his relationship with Irglova and on their shared love of music – charmed the Sundance Film Festival and became an art house hit around the world. And it was a perfect forum for Hansard's songcraft – which had been very well known in Ireland thanks to the years he spent fronting The Frames, but not so much abroad.
"The film was made in a few weeks with a pair of Handycams," he says. "We thought it might have some resonance in Ireland, but we didn't for a moment imagine it would lead to this huge thing. I mean, the musical is just so much bigger now – in retrospect, it feels as though John's film was just a demo for what people experience on Broadway and the West End."
Hansard has seen Once: The Musical "10 or 12 times" and says he has tried to divorce himself from the story that unfolds. "It's not like" – here he adopts a grand, authoritative voice – "the Glen Hansard Story. I certainly don't see it as such, although, there are snatches of dialogue that are uncannily like the sort of things me and Mar used to say to each other."
Falling Slowly's Academy Award win ensures it enjoys a special place in the Hansard songbook, but even without the golden statuette, the tender, uplifting ballad would surely last the test of time.
"The older you get, the more you want to leave behind work that will endure. I'd love to have maybe 10 songs that will outlive me. I'm pretty sure Falling Slowly will do that. It feels like it's gone out into the world on its own."
Fragments of the song percolated in his mind for years before it was written. "That line: 'I don't know you/But I want you all the more for that' came into my head one day and I liked it," he says. "I kind of knew it would find its way into a song at some point because the words kept coming back to me.
"It was maybe the first song me and Mar wrote. I was in her house in the Czech Republic and I put the line out there and I had the opening few bars and it grew from there in much the same way that you see in the film and the musical."
Just two days before we speak, Hansard played a well received show at Glastonbury. "I've played it maybe four or five times and there is something very special about it. Maybe it's the lack of cynicism you sense there or the fact that the punters seem to be on your side, willing you to do your best.
"Playing festivals can have its ups and downs and sometimes you can't win over a festival crowd no matter how hard you try and, of course, there are occasions where you just aren't on song and there's little you can do about it."
Last month, Hansard realised a life-long dream by performing with Joni Mitchell. The great songwriter hasn't played live in many years, but was convinced to take part in a commemorative event to mark her 70th birthday in Toronto.
"I had been invited to play a Joni tribute concert in the Hollywood Bowl a few years ago and I was like, 'I'm there – but I want to play [one of her standout songs] Coyote.' I was told afterwards that she had been at the show and had liked my performance. I can't tell you how much that meant to me.
"So, a couple of weeks back, I find myself in rehearsals with all these great musicians and Joni herself shows up. We didn't expect her to sing, but she did – and she sounded great. I was sitting at the side, taking it all in, and she sees me and calls out 'Glen' to me and I'm thinking 'Joni Mitchell knows my name!' And then she's over to me to talk about one of her songs and how she would like me to sing it: 'It's all about timing and phrasing,' she said, and I'm thinking to myself: 'Joni Mitchell is giving me a singing lesson.' Oh man – moments like that will stay with me for the rest of my life."
Later this month, he will rub shoulders with another iconic figure in music when he supports Bruce Springsteen at Nowlan Park, Kilkenny. "These people were my heroes, man – Cohen, Dylan, Springsteen, Mitchell. Now, getting to share a stage with some of them or collaborate in some way ... I have to pinch myself sometimes to make sure all of this is real."
The Glen Hansard of 2013 cuts a very different figure from the sometimes truculent soul who fronted the Frames in the late 1990s, early 2000s. One of the things that made him so compelling at that time was how he channelled his frustration about not receiving recognition into his songs, particularly those on the spirited Fitzcarraldo album.
"I never pretended that I didn't care if our songs were heard or not," he says. "I came from a place where I wanted as many people as possible to hear the music. I had no empathy with that whole art school idea of making music for yourself and if anyone else heard it, it was a bonus. I could never understand that mentality.
"Even in my darkest days, I did imagine that one day those songs would be heard and we would get to the next level. If I hadn't thought that, I might as well have given up there and then."
It was, Hansard says, all about little steps. "First, as someone from the Northside (of Dublin), it was about going over O'Connell Bridge and having the balls to busk on Grafton Street. Then it was about playing London. Then it was about getting to New York. The scale should be shifting all the time."
He has already begun work on a second solo album, although he says he wasn't pleased with the songs that he recorded with Thomas Bartlett – producer of Rhythm and Repose – some months back.
"It's no reflection on Thomas – I'm just not sure the songs were ready. My gut was telling me 'no' and I always listen to it."
He has no plans to record the first Frames album since 2006's The Cost.
"All those lads play every show with me, so it is the Frames to some degree, but right now I have to follow my vision – maybe be a bit ruthless – and see where it takes me. Much as I love the lads, you do want to work on your own or with other people every now and again.
"You can't let that creativity stagnate."
Glen Hansard plays The Iveagh Gardens, Dublin on July 21 and Galway Arts Festival on July 25, www.galwayartsfestival.com