"I lived in ballroom dancing for three and a half months," Patridge told PEOPLE over the phone Tuesday. "I didn't do anything else."
Now The Hills alum is passing on a few words of wisdom to former costar Kristin Cavallari, who will be sashaying onto the dancefloor with Mark Ballas on Sept. 19.
"I actually talked to [Kristin] last week," says Patridge, who is also the new face of Bremann Research Labs's skincare line. "She texted me, and she was like, 'Hey, I was just thinking of you, and I wanted to tell you I'm doing Dancing with the Stars. It's going to be fun, right?' "
"And I was like, 'Yeah, you're going to have an amazing time! You'll be in the best shape of your life.' "
Patridge, 26, who suffered injuries and a bout with the flu during her stint on the show, had this advice to offer her fellow MTV alum: "I told her it's going to get hard, but just have fun with it. … I had a blast."
"Ballroom dancing, it's totally different than just going to a club and dancing, so it takes a lot of commitment and dedication," she says. "You really have to live in the dancers' world."
How does she expect Cavallari will hold up this season? "I don't know," she says. "I think she’ll do well, though."