He told The Sun: "I'm enjoying my football and that is showing in my form for QPR. This game is all about confidence and if you're in the team one minute and out of it the next, you're never going to be at your best. I had three years at Sunderland and in that time we progressed from being a yo-yo club to an established Premier League side who finished in the top 10 last season.
"It was fantastic to be a part of that achievement but it was also frustrating because I wasn't playing as much as I wanted to.
"We signed a lot of big players in the summer including Wes Brown and John O'Shea and we still had Michael Turner and Titus Bramble, who were also ahead of me in the queue.
"A lot of people doubted that I'd get in the team but I played in Sunderland's first four games of the season and I was totally committed and played with my heart on my sleeve.
"The reason I left Sunderland was because I was in the final year of my contract and they told me they weren't going to renew it.
"That was a pretty clear sign that my time there was up and as soon as I spoke to Neil Warnock at QPR my mind was made up.
"Being back in London was an attraction but the key thing for me was the manager and the ambitions he had for the club.
"We're a team with a lot of new signings that is still getting to know each other. We're trying to become a Premier League club again but we're a long way from that yet."