Kewell, who took charge of Notts following a rather successful stint with Crawley Town, was sacked just 14 games into a three-year-deal last month.
The cashed up League Two club paid Crawley more than A$200,000 for the 40-year-old's services but quickly pulled the trigger after a winless seven-game stretch left them languishing inside the relegation zone.
"It's a difficult pill to swallow, I've still got to wrap my head around what happened," Kewell told the Herald Sun.
"You’re doing so well somewhere (Crawley Town) and at that level to get bought to put your own stamp on something and change it.
"Then to be (sacked), it knocks your confidence and it makes you reassess your methods.
"It’s frustrating, I know I can do it. It paints a picture that I failed. I’m sure most people fail if they only got 11 (league) games and no window to bring players in."
While successive departures have headlined the Socceroos legend's brief coaching career, Kewell vowed to use his experiences as a tool to develop his methods in time for his next appointment.
"I’m more determined than ever to continue. Hopefully I get another opportunity to coach, you want to learn from your mistakes," he said.
"I’m regrouping, working on a few things, still coming up with training ideas, still working on the next step-ups to the way I want to play and how I can introduce it.
"Just prior to being sacked I put together another sequence of training sessions. I’m always trying to evolve my sessions.
"Now I have to wait and start again, wherever I get another chance, and quickly progress the style."
