Kennelly's team was down by two goals at the main break, and with Roo pair Brent Harvey and Ed Lower causing damage on the field, the playing group spoke about the need to take the game by the scruff of the neck.
"We kind of knew the game was there for the taking if we'd just stepped up as an individual and not waited for someone else to actually take it," Kennelly said on Wednesday.
"I said that numerous times at half time -- 'just grab it, just grab it, grab the game and take it on' and that's what we did.
"The second half was probably our best second half of this year."
The Swans slammed on eight goals in the third quarter and a further five in the final term to end North's season.
Kennelly says the Swans first half against the Roos was down to the Swans "reactive" mind-set.
"I suppose we missed Goodsey around the stoppages but Jarrad McVeigh stepped in and became very pro-active and really [went] after the footy.
"You rely on players like that to go after the footy when you've got so many players, I suppose, who like to be defensive and like to be re-active, it's good to guys like Macca in there."
Kennelly said the last two months of the season were frustrating as the Swans searched for answers to a form slump that saw them with just two wins from eight games going into round 22's win over the Lions.
"We tried everything. More training, less training, different times, different training techniques … It's not easy to get it back but I suppose the only thing you can do is work hard."
Looking ahead to Friday night's clash with the Bulldogs in the semi-final, Kennelly was keen not to say anything to inflame the Bulldogs just two days before the big game.
"I've been doing this for a few years so I'm not going to start giving you anything," he said with a laugh.
"They've been copping it from people like yourselves (journalists). We've copped it too so the best way to come back is to play good, hard, contested football."
The Sydney Swans final against the Western Bulldogs will be broadcast live in Sydney on Channel 7, from 7:30 PM.
