Although the 28-year-old singer co-wrote the track, he almost didn't end up singing it on the soundtrack to the movie 'Furious 7' because he "didn't fit the profile of 'The Fast and the Furious'" franchise.
He told British GQ: "It was very early on when they told me that I couldn't sing 'See You Again' because I didn't fit the profile of 'The Fast and the Furious', AKA I wasn't cool enough and I had goofy music videos. I hadn't even signed my deal yet, but I called them up and said that I wasn't going to give them the song, then I hung up and miraculously, one week later, I'm singing it."
Charlie also revealed he has had some tough times in his career, including when a songwriter he admired told him his lyrics were terrible in 2012.
He said: "In September 2012, a successful songwriter told me, pretty harshly at the time, that my lyrics sucked and that if I wanted to be better I really needed to hone in on becoming a stronger lyricist. It wasn't the easiest thing to swallow at the time, but it ended up being really beneficial."
However, Charlie finally started to believe in himself after he wrote the 2016 track 'We Don't Talk Anymore'.
He said: "I think when I wrote 'We Don’t Talk Anymore', I felt like I was pretty good, because I thought that pre-chorus melody was clever. People actually didn’t really like that song when I first played it for them, the label wasn’t really feeling it, but I just knew it was catchy."