If there was one overriding message to be found in Frank Warren’s appearance Friday night at the Michigan Theater, it was this: If you have a secret, share it. Your world, or someone else’s, could become a better place.

“Free your secret and become who you are,” he said.

Frank Warren is founder of PostSecret, a community art project he started five years ago that has since blown up into an online phenomenon in which nearly 500,00 people from around the world have shared their deepest secrets via postcard. The cards are displayed on Warren’s blog, PostSecret.com, and are also the subject of five books.

During the 90-minute program, which was well-attended by a mostly college-age crowd, Warren talked about how PostSecret got started. “Trust your crazy idea,” he advised the crowd. “It might be your destiny.”

Warren also shared some of his favorite post cards — including some that couldn’t be published, for various reasons. Beside post cards, he said he’s received secrets on seashells, bananas, a sonogram and even a death certificate.

Microphones were provided so audience members could share their own secrets, which ranged from humorous to heavy. More than one person shared thoughts of suicide. One speaker sent well wishes to the person in his youth who outed him as a gay man, saying the abuse he endured at the hands of other students made him stronger.

The show, part of the Ann Arbor Conversations Series presented by Michigan Radio, opened with part of the music video “Dirty Little Secret," from the band All American Rejects; then Warren talked about how the use of some PostSecret material in the video wound up raising money for National Hopeline Network, a suicide hotline.

Warren said that every day each of us has a choice “to bury our secrets in a box or bring them into the light and share them like a gift.”

Once we open ourselves up to secrets, “inside there’s a kernel of knowledge you can learn and grow from,” he added. “Sometimes when we think we’re keeping a secret, it’s actually keeping us. … The act of sharing a secret can be transforming.”

Warren sent a shout out to Ann Arborite Davy Rothbart, editor and publisher of Found magazine, who was in the audience, and said Found was an inspiration for PostSecret.

The Michigan Theater event coincided with the publication of Warren’s fifth volume, “Confessions on Life, Death, & God,” which was recently No. 1 on the New York Times best-seller list.

After his presentation, the long line of fans seeking to have their copies autographed ran all the way from the theater’s stage to the lobby.

One of those in the queue was Nik Thakur of Toledo, who said one of his secrets is included in Warren’s new book.

“I thought it was probably one of the most surreal things I’ve heard,” he said of the program. “It was a rollercoaster. I got goosebumps. I was about to cry (and) I don’t cry. I’ve been following this project since 2005 and it’s the first time I’ve been so excited.”

He said he felt that being in the audience gave him a sense of belonging. “Every person in this room is here for PostSecret. It’s something I love and most of these people love too.”

Ann Arborite Alison Fendrick was similarly impressed. “I thought it was really moving. I’ve never felt so close to such a huge group of people that I don’t know. Some of the secrets really break your heart. It really is life-changing.”

Although she’s never actually sent in a secret, Fendrick admits she’s considered it. “I think about it when I go to bed, I think about secrets I would potentially send in, but then I never get around to it … but I read the (PostSecret) site every Sunday.”

Kendall Ufer of Ann Arbor, who said she mailed secret to Warren during her junior year of high school, was also in the autograph line. “I think it’s nice to share something you’re dealing with yourself with complete strangers,” she said. “You can share it and know that people read it. It’s nice to write it down and say ‘this is what I’m dealing with.’”

So what is it about Warren that makes people feel they can trust him with their deepest secrets, even though the process is anonymous?

“He’s like a blank slate,” said U-M student Devon Perry. “He’s someone so ordinary you feel like you could talk to him.”

Roger LeLievre is a freelance writer who covers entertainment for AnnArbor.com.