The former UFC welterweight champion suffered the most shocking upset in UFC history when Matt Serra -- who needed to win a reality show to earn a title shot -- scored a first-round TKO finish at UFC 69 in 2007.
St-Pierre had some close calls, but went on to win 12 straight in the Octagon before stepping away in 2013.
"It's unfortunate for Ronda but I'm happy for Holly in the same time," St-Pierre told Neil Davidson of The Canadian Press."In this game, no one's invincible. Sometimes you zig when you should zag."
In Rousey, St-Pierre sees someone who has the potential to make just as strong a comeback as he did.
"I needed to beat a lot of my own demons, a lot of my fear," said St-Pierre. "And I came back stronger. So in a way for Ronda it's sad that she lost, but maybe it could be the best thing that ever happened to her, in that she will come back much stronger.
"It taught me what it takes to become world champion. And when I lost to Matt Serra, it taught me what it takes to stay world champion."
St-Pierre leaned heavily on the help of a sports psychologist to rebuild his own confidence, but also admits he may have bought into his own hype a bit too much.
"You know when you become world champion at 25 years old and everybody around you -- in the gym, everywhere -- tell you how great you are and things like that, it makes you believe that you're in a box that separates you from the other fighters.
"But this box, this line is an illusion. And that's what happened. Even though I'm not a cocky guy, I got caught in those situations, many other things. I made many mistakes."
5 MUST-READ STORIES
Chill. UFC women's bantamweight champion Holly Holm says everyone shouldn't bash Ronda Rousey because most "wouldn't even have the nerve" to fight.
A preview of the behind the scenes footage at UFC 193.
Holly Holm is already hanging out with celebs.
Highlights from open workouts in Monterrey.
Holly Holm hits the cringe circuit but her interviews are great.
A huge montage of Fabricio Werdum's workouts.
Mauricio Rua being fed a ton of Korean food.
Gina Carano's new movie 'Extraction.' (might be NSFW)
#WSOF25: Prefight Show (this is pre-reshuffle chaos but still interesting)
Here we go.
Gonna be tough.
I'm not! I'll be fine. Thanks for ur concern tho! https://t.co/ZOfsMf5L3d— Daniel Cormier (@dc_mma) November 20, 2015
Gunnar Nelson (@GunniNelson) November 20, 2015
Chris Weidman (@ChrisWeidmanUFC) November 19, 2015
Ready for who?
Sage Northcutt (@sagenorthcutt) November 19, 2015
Cody Garbrandt (@Cody_Nolove) November 20, 2015
You could take him.
Train like your STRONGER FITTER evil-twin is plotting to kill you.— Be Healthy (@BeHeaIthy) November 18, 2015
Rich Franklin (@RichFranklin) November 20, 2015
Just hanging out!! https://t.co/j9lAT6ofNP— Cowboy Cerrone (@Cowboycerrone) November 20, 2015
Announced yesterday (Nov. 19 2015)
cancelled Brian Cobb vs. Mike Ricci at WSOF 25
cancelled LaRue Burley vs. Joe Condon at WSOF 25
cancelled Benny Madrid vs. Ramil Mustapayev at WSOF 25
Joe Condon vs. Mike Ricci at WSOF 25
LaRue Burley vs. Ramil Mustapayev at WSOF 25
Found something you'd like to see in the Morning Report? Just hit me up on Twitter @SaintMMA and we'll include it in tomorrow's column.