Bardsley was frozen out under the Italian following incidents on social media and failed to make an appearance for Di Canio this season.
However, the defender has featured five times under new head coach Gus Poyet, scoring in his last two games, and believes there is new positivity at the Stadium of Light.
"The things that happened were so disappointing," Bardsley said of his bust up with Di Canio.
"The supporters probably don’t know the full extent of what happened over the summer. It’s history now. There's a new manager, a new lease of life and I’m loving playing under Gus Poyet.
"I thought at the time my Sunderland career was over but the manager has come in, he's given me a new lease of life and here we are talking about a 1-0 win over Manchester City. It's mad."
Sunderland's success against Manchester City made it three wins in five games under Poyet, who has lifted the club off the bottom of the Premier League.
Bardsley believes his mental strength helped him cope with not playing under Di Canio.
"Thankfully for me, I'm quite tough upstairs so I stayed strong," he continued.
"I knew that I had to offer this football club a little bit more than I had at the time.
"I went over the advertising hoardings against City and I think a couple of people in the crowd patted me on the back. That was nice. A few months ago I would probably have got chinned."
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