The 'Oh My God' hitmaker admits he only realised he didn't want to lose the group when drummer Nick Hodgson quit in December 2012.
He recalled: ''Personally, a few years ago I got a little bit lazy and stopped taking as much interest in it [the band] as I should.
''I think my ambition meter got full and I thought I'd done everything, ticked all the boxes.
''Nick, my best pal and drummer left and I suddenly realised I didn't want to live without it [the band]. It gave me a kick up the a**e. I can't speak for the rest of the band but I think it gave us all the same kind of feeling.''
The singer admits he felt ''scared'' at the thought of not performing on stage anymore as he ''needs'' the band in his life.
He added: ''I was scared at the prospect of not playing live anymore. I really need it and enjoy it. [The band] is thing I've always wanted to do.''
This Doctor won't be saying 'goodbye' in the same way as those who have left the series in recent years.