Tua in into his fourth week of training for what has been billed as "New Zealand's fight of the century" against fellow-New Zealand heavyweight Shane Cameron in Hamilton on June 6.
It will be the former world title challenger's first bout since September 2007, when he stopped American Cerrone Fox in the second round of a mismatch.
Tua, 36, agreed with the view that he seemed far more motivated than during his comeback from a previous period of inactivity four years ago.
"It's the feeling that was there for a long time as a youngster coming up," he said.
"Then it went elsewhere, for whatever reason.
"It took a long, frustrating time to find it, but it's here to stay and it's important to hold on to it. I'm loving it. I'm really passionate about the sport now."
In March 2005, after two years out of the ring, Tua stopped American Talmadge Griffis with 25 seconds to spare in a 10-round contest in Auckland.
He has won his six other outings since then as well, taking his record to 49 wins, 42 by knockout, three losses and a draw.
His biggest moment in the sport remains his unsuccessful world title shot against Briton Lennox Lewis in Las Vegas in 2000.
In recent years, however, he has been in the news more for a court battle with former manager Kevin Barry and financial manager Martin Pugh than for his exploits in the ring.
The Apia-born Aucklander said the showdown against Cameron "means everything really" at this point of his career.
"I've been inactive and Shane has been active, and I look on Shane as the man to beat to get back to having a real goal," he said.
"It's important that I beat the guy who is seen as the guy to beat, so really this fight means a lot. It's important to win this fight and to win it well."
After his layoff, Tua admitted that going back into camp had been tough.
"The first week, I was walking like an old man, but it's been really good to get back into hard training," he said.
"It hasn't been an easy start. It's the real stuff."
Tua was confident that his conditioning would be spot-on against Cameron, despite opting not to have a lead-up fight and focussing instead on his training.
"I'm not saying that in a boastful or arrogant way," he said.
"But the way things are now, it's important to have the right preparation."
Before concentrating on Tua, Cameron, 31, has a "homecoming" fight in Gisborne next week, when he will look to add to his 22 wins, 19 of which have been by knockout.
Beaten just once in his career, the "Mountain Warrior" will be up against American Robert Davis, who has a 32-9 win-loss record.
