On the September 6 episode of 'Yoo Hee Yeol's Sketchbook', he revealed, "Before, I used to be able to write 3-4 songs in just one sitting. But recently, I take a month to write one song, and I keep editing one song that I wrote 1 year ago."

SEE ALSO: Actor Song Jae Rim unexpectedly passes away at 39

But apparently, it was a happy conundrum! He revealed, "When I was a trainee, I kept writing songs because I tried to get rid of all the tiring things and things that were building up, but I think right now I'm this way because I'm so happy."

He also added, "I don't listen to my previous songs because I become embarrassed. If I record 'Heartbreaker' again, I wouldn't sing it like that. I'd pronounce everything in a correct manner. I was really worried and stressed as I prepared my solo album. I had the mindset that it was going to be my last album, so I put in everything I wanted to do."