The boyband finished second to Alexandra Burke in the 2008 edition of the show, and despite initially being "devastated" by the result, they soon realised the benefits of shopping around for a record deal that was right for them.
"When we didn't win The X Factor we were totally gutted," Aston Merrygold told The Mail On Sunday. "We thought we were going to win.
"In the hour after the result and the show ending, we got together, knocked on Simon's dressing-room door and begged him to sign us. He wouldn't because his policy was only to sign the winner.
"It was devastating. We had to pick ourselves up and look around the business and make our own deal with a record company. Looking back, it was the best thing that could have happened."
Merrygold's bandmate Marvin Humes added that JLS had never shied away from the hard work required to make it in the music industry.
"Each one of us was hungry and focused to succeed," he said. "Yes, we wanted fame, yes we wanted money and success but we always knew it came at a price. I think if any of us didn't know exactly what we were doing, we wouldn't be sitting here.
"This isn't a band, it's a business. It's our business and each of us works at it 24/7. That's the deal. None of us is stupid, each of us knows it could all end tomorrow so we have to maximise what we have when we have it."
JLS returned to The X Factor last night (December 10) to perform with One Direction at this year's Wembley Arena final.
> JLS unveil old rehearsal footage for new 'Eyes Wide Open' DVD - video
Watch JLS in the video for 'Do You Feel What I Feel?' below: