The Greece international is out of contract in the summer but is yet to agree to a new deal with the Glasgow giants.
The former Manchester City man, who arrived at Parkhead in 2008, is still pondering the idea of continuing his career with the Bhoys who he says he owes a lot to.
"I'm not thinking about my contract ending. You have to honour the contract you have signed. If you start thinking about leaving, you can lose your focus easily and then you lose the confidence of the manager and your team mates," he told Greek TV programme SuperBall.
"I've been through a lot with this team and my only thoughts at present is how I achieve the team's aims.
"Money has never been a motivating factor in my career because I could have left Celtic and signed for a team with more money. I've had offers, most from teams in England, who have offered me more money than I was getting at Celtic.
"That proves I've always put money into the background. How will things develop? I don't know but as I have said before, I owe a lot to this team.
"Celtic have been my team for the past seven seasons. They have helped me change my mentality as a footballer.
"They've won titles and made me feel like a winner. I don't know what the next stage of my career will bring but I enjoy my football here."
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