The flanker was named skipper on Tuesday after last year's co-captain Juan de Jongh tore knee ligaments and faces up to three months on the sidelines.
Kolisi made an instant impact when he came into the Stormers side in 2012, but when his career failed to take off he needed a few home truths from coach Robbie Fleck to spark a change in his attitude towards preparation and training.
Advice heeded, the 25-year-old is now ready to live up to the expectations that come with being one of the senior players in the team.
"I had a conversation with the coach last year and he told me I had to grow up, basically," Kolisi told Reuters in an interview. "Since that day I haven’t looked back.
"It’s not been easy, it’s been tough. I won’t lie, I had to mature a lot.
"Obviously, now I’m a leader at home as well, I have got three kids that I must be a role model for. I had to change a lot of my ways."
The Stormers have lost a number of key players in recent seasons but Kolisi, who has collected 16 Springboks caps since making his debut in 2013, says their presence is still felt.
"I have learnt a lot from those guys that have gone, Schalk (Burger), Duane (Vermeulen) and Jean (De Villiers)," he added.
The Cape Town-based side have a challenging fixture list this season including all five of New Zealand's Super Rugby teams.
Last year, they reached the quarter-finals having played only South African and Australian sides, as well as the debutant Sunwolves from Japan and Argentina's Jaguares.
They were given a sharp reminder of just how far ahead the New Zealanders are in a 60-21 home thrashing in the playoffs by Waikato Chiefs.
Kolisi said the competition format left the Stormers under-prepared for that game and that playing teams from New Zealand earlier this season would bring long-term benefits.
"It means we won’t get to a playoff like we did and get shocked. When you play them early in the competition it’s perfect," he said.
"But you have got to be ready mentally. We are not afraid because we have to play them. If that is what it takes to win Super Rugby, so be it."
Kolisi is convinced that the Stormers, who start their season with a bruising North-South derby at home to the Bulls on Saturday, are genuine title contenders.
"I wouldn’t be here if I didn’t think that, I wouldn’t have worked this hard in pre-season if I didn’t think we have the squad to do it," he said.
(Editing by Ed Osmond)
