The 'Black Parade' rockers split in March 2013, and the frontman admits he knew it was time to call it a day because the band was making him ill and affecting his personal life.
He said: ''It was one of those things that actually was painful and slow, a sequence of breaks. But it comes down to me just being really depressed.
''It's hard to go into too much detail about the mechanics of it, but one day I just said, 'You know, we can't do this.' It was really hard. Nobody was happy. I wasn't happy.
''I felt like I was in this thing that I couldn't get out of, because I was partially responsible for other people's lives. And then it started to make me physically sick, and it started to affect my personal life.''
Gerard feels he has been able to move forward since leaving the band, and though he didn't plan a solo career, he has been working hard on a new album.
He told NME magazine: ''Being in a band holds you in stasis. There's a refusal to grow past a certain point and I personally stopped growing.
''I guess I thought I was going to have a 'normal' life after My Chemical Romance, but then all of a sudden I started to plan out what a solo career would be like.
Corgan took to Instagram to confirm rumours of new Pumpkins material, saying the first songs could arrive as early as May.