The former Rangers captain feels he's in the best form of his career.
He said: "I'm so happy, I've settled in so well and the fans have took to me.
"You've always got a concern at the back of your mind but as soon as I walked through the doors I realised that this is a great bunch of boys.
"Everybody says to me now that I look more chilled out and I'm a lot happier because obviously the last six months of my days up in Scotland weren't my happiest. I made the right decision (to come to Birmingham).
"I'm happy, happy in my football and hopefully Birmingham will benefit from that."