Crystal Harris in Tears Over Broken Engagement to Hugh Hefner

Saturday, June 18 was to be the happiest day of Crystal Harris' life. That was the date set for thePlayboy bunny's wedding to Hugh Hefner until Harris broke off the engagement. ET's Chris Jacobs sat down with Hef's 25-yr-old former fiancee for details of the split straight from the source.

Through tears, a newly single Harris confides that although she is "relieved," she feels her biggest regret in breaking the engagement was that she "disappointed everybody."

"It happened so fast," she says of her decision to marry Hefner, admitting that the glamorous whirlwind of fame played a large part to what (in retrospect) may have been a hasty decision. "Hef asked me to marry him in front of three cameras and a photographer," Harris explains. "I thought it was something I wanted."

Although Crystal tells Chris she "wouldn't trade [her time with Hefner] for the world," she "needed to be true to [her]self."

Hefner announced the cancellation via Twitter on Tuesday, writing, "The wedding is off. Crystal has had a change of heart."

Likewise, Crystal took to her Twitter page, leaving this comment: "After much deep reflection and thought I have decided to end my engagement with Hef. I have the utmost respect for Hef and wish him the best going forward. I hope the media will give each of us the privacy we deserve during this time."

The break-up comes as Harris covers the July issue of Playboy captioned, "Introducing: Mrs. Crystal Hefner." However, in light of recent events, Hugh tweeted a photo of the following revised cover which now has a warning sticker that reads, "Runaway Bride in This Issue."  The issue hits newsstands Friday.

Watch the video to hear even more from Crystal Harris in her own words.