Voted Australia's greatest ever player in 2012, the 35-year-old admits he feels a sense of unfulfilled potential as he calls time on a career blighted by injuries
However, the veteran was unable to sustain his fitness, missing nine games of the 2013-14 campaign so far with a combination of injuries, while Heart's dreadful season (just six wins in 24 matches) did not aid his cause.
Speaking at a press conference, Kewell - voted Australia's greatest ever player in 2012 - admitted to sense of unfulfillment following a long career blighted by injuries.
"I do sit there with my wife and my close friends and wonder, what if? Yes, I feel like I can play the game, I understand the game," he said.
"And I wonder if I didn't have those injuries, what could have been? But I believe the path was set out for me and I think it's made me a better person.
"I've been at the highest level in football but I've also been at lowest level. I understand where the good and the bad does come from. And I think it's made me a better person all round."
Kewell, who won 56 senior caps for Australia, nominated his goal against Croatia which sent the Socceroos into the knockout stage of World Cup 2006 as a career highlight.
"You get that asked a lot as a footballer," he said.
"People go, 'what's the moment, what's the greatest goal that you've scored?'
"You know what? Every goal is. It doesn't matter whether it's one that puts your country through or one that saves you from relegation or one that wins you the title. Every goal you score is special.
"But, in saying that, the one against Croatia was special. To be able to score a goal in a World Cup in the biggest level in football was fantastic."
Kewell also admitted he did not expect to earn a place at the 2014 finals with his brief stint at Heart, claiming it is time for the younger players to take the limelight on the international stage.
"I always said it's a pride, a privilege, an honour to play for your country and I think you've got to be playing at the highest level to being do that.
"I had a year out, I came back. Yes I played well for Heart in the games that I've played. I've had some injuries this year. I think it is time to pass on and let these youngsters step up and be counted for."
Kewell made his professional debut with Leeds United in 1996 at the age of 17.
The scintillating winger was named the English PFA's Young Player of the Year in the 1999-00 season as he helped Leeds to third in the Premier League with 10 goals and 13 assists.
At the end of the 2002-03 season, Kewell moved to the club he supported as a youngster - Liverpool - but never cemented a position at Anfield due to a myriad of injuries.
Stints followed at Galatasaray, Melbourne Victory and Al Gharafa prior to his final spell with Heart.