Tierney was linked with a move to the Gunners for the duration of the summer transfer window.
The move was completed on deadline day, meaning the full-back had a tense few months of not knowing whether it would go through. But he insists that he remained calm throughout the process.
He said to the club's official website: "It's been fine for me.
"I've been working hard in rehab and I've had good people around me as well. It's been easy for me.
"At Celtic I was training hard, working hard and just looking to get back fit.
"That was my main focus."
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