Cowan (30) announced yesterday he had signed a two-year contract with the Gloucester club in England, saying he was looking forward to the next stage of his career.
"I had a few offers on the table but Gloucester sold it to me.
They are a passionate club with a lot of potential and that sort of reminded a bit of down home with the way their fans are and the support the club has," Cowan said.
"I've come to the stage to move on for my career and it is a great chance to experience another part of my life. In the end it wasn't a hard decision to make.
"It is part and parcel of the game these days. People come in and people go. You have to accept that and move on."
Cowan notched his 100th cap for the Highlanders in the match against the Stormers and is sitting on 93 caps for Southland.
He would like to play another season for Southland to play a century of games for the province and is not needed by Gloucester, which sits mid-table in the premiership, until October.
"Obviously that is the goal and that is something I would like to do - to give something back to the people who have supported me all through the years. But what will be, will be."
He still has to concentrate on the rest of the Highlanders campaign, starting with the Blues on Friday night at Forsyth Barr Stadium.
Cowan has come a long way since making his debut for the franchise in 2003, coming on as a replacement winger.
He was captain of the side in 2009-10 and skated on thin ice in 2008 when he was arrested three times after alcohol-related incidents in Invercargill and Dunedin.
Slapped with a booze ban by the NZRU, Cowan bounced back to remain in the All Blacks and played in his 50th test last year.
"It is not something I regret.
For if I had not made those mistakes then I wouldn't have learnt from then. And I learnt a lot. I would like to thank the New Zealand Rugby Union ...
and the coaches Graham Henry, Steve Hansen and Wayne Smith, who stood by me and helped me out."
