BERLIN (Reuters) - British singer Ed Sheeran said on Friday that the hardest part of songwriting was coming up with lines that had never been written before as a new documentary detailing his creative process premiered at Berlin’s international film festival.

The movie “Songwriter” was directed by Sheeran’s cousin, Murray Cummings, and follows the Grammy winner as he travels around the United States and England writing songs on his laptop, jamming in a garden and recording in the studio.

The intimate portrait of Sheeran, who was the most-streamed artist on music service Spotify globally in 2017, includes footage of him belting out songs while crossing the Atlantic on the Queen Mary 2, returning to high school to see his music teacher and talking to his father about his songs.

“I think the most difficult thing to do with writing a song is finding a phrase that you haven’t heard before because there’s always a song that’s going to be like: ‘I love you baby like crazy, I miss you maybe’,” Sheeran told a news conference.

He said he had learned not to push himself if he was struggling to write and did not believe writer’s block existed.

“What I do when I can’t write a song is I just put the guitar down and go and do something else for about a couple of weeks and then come back and then I’ll be able to write a song,” the 27-year-old said.

“So the way that my mind is now is, I will be able to write songs forever - they probably will start being about pretty mundane things because my life is getting more and more calm.”

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Sheeran said he liked the documentary because it showed a song being written from start to finish, rather than just an album being recorded.

“I like that Murray found a niche that hasn’t really been done before. It’s quite difficult to find something that hasn’t been done in a music movie,” Sheeran said.

Sheeran, who said he planned to make a film next year in which he would play something other than himself, listed “Goodfellas”, “Cool Runnings” and “Love Actually” as his favorite movies.

Cummings told Reuters the documentary would give fans an insight into Sheeran off-stage.

“When he’s on his own he’s kind of very like relaxed and chilled and stuff. So I think they’re going to see that’s what he’s like because this film just kind of shows what I see every day,” Cummings said.