Justin Timberlake on Master Class: Going Solo Was Bittersweet, I Felt Music Changing

Justin Timberlake says leaving 'N Sync behind was one of the best and worst things he's ever done.

Appearing on "Oprah's Master Class," the former "Bye Bye Bye" singer admitted that he felt the need to move forward not just because of an urge, but because music was changing.

"Why wouldn't you ride this out? You're the biggest group in the world. Why would you walk away from this? It's one of the best/worst things I have ever done. It was bittersweet. It was hard to kind of say goodbye to that era. But I felt it changing. I felt music changing. I felt myself changing," Timberlake told Oprah's Master Class.

In a second clip below, he said "Sexy Back," despite being a big success in his solo career, was hard to get off the ground because people couldn't believe it. They thought it was a joke.

"Oprah's Master Class" airs tonight, Sunday, at 10 p.m. on OWN.