It may be a paradox, but it's a commonly offered pearl of wisdom about living happily ever after: When it comes to settling down, don't settle.

That's what now-single Jen Schefft, former fiancée of "The Bachelor" Andrew Firestone, is telling other uncoupled women these days.

"Settling means being in a relationship that's anything less than you deserve," the 30-year-old Schefft, author of "Better Single Than Sorry: A No-Regrets Guide to Loving Yourself and Never Settling," said in a phone interview. "It's being in a relationship that's not exactly right … for the sake of being in a relationship."

Speakout! Should People Settle in Marriage?

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But it is possible to take the popular mantra too far — straight into unrealistically high standards territory.

"That phrase is too black-and-white," said Whittier College psychology professor Charles T. Hill, co-author of The Boston Couples Study, which followed the progress of several couples over a 25-year period. "You're never going to find anybody who's perfect. You're going to have to settle for less than perfect."

That said, we all know people who claim to have found their "perfect" match. And we all know people who settled down with mates they weren't totally in love with or settled for unhappy relationships because it seemed safer to be a two than a one.

Schefft has firsthand experience with trying to make something work that just wasn't right. At the end of the ABC reality show "The Bachelor," tire heir Firestone proposed to her on national television — and she said yes.

The reality star quit her job in Chicago, moved to California to be with Firestone and worked with him at his family's winery, despite the fact that she'd only known him for a few months and much of their whirlwind relationship had unfolded on camera.

"It wasn't the right fit for sure," Schefft said. "I gave up my life. It was something I didn't give a lot of thought to."

After the couple split, Schefft — who's now back in Chicago working as a PR account supervisor — said she "got a lot of flak" for the breakup.

"Just because someone is rich or an heir to this tire fortune doesn't make it a perfect relationship," she said. "Some women would have stayed, but no amount of money or status is going to make you happy."

Two years later, Schefft went looking for love on TV again as "The Bachelorette" and turned down both of the final suitors — fielding a barrage of criticism for a second time.

Those who followed the series said "I must be so picky and nothing's ever right for me," Schefft remembered. "A lot of people were mad at me."

But she stands by her belief that it's better to be alone than with someone for the wrong reasons, and encourages women not to panic about being single.

"There's a difference between a really good relationship and a relationship of convenience," she said. "'Don't settle' doesn't mean the guy you're with has to be absolutely perfect. It's about waiting for the right person for you."

Still, relationship experts warn against having lofty ideals about marriage and waiting too long for the right person — since no one is 100 percent "right."

"People now have higher expectations of marriage — maybe too high," said Hill. "We expect our spouse to be our best friend and marriage to meet all of our needs. One person can't meet all of our needs."

Marriage gurus worry that living by the "don’t settle" philosophy could sabotage the hunt for a suitable spouse.

"You never find Mr. or Mrs. Perfect Right," said David Popenoe, co-director of the National Marriage Project at Rutgers University. "A lot of this is wrapped up in the idea that there's one soul mate out there. That is a terrible idea. Each marriage is an adventure. Settling, in a sense, is a part of life."

One Kansas City writer thinks women are more guilty of throwing around "unsettling" advice than men.

"No guys ever say 'settle' or 'don't settle,'" said late-30s singleton Hampton Stevens, who has a girlfriend. "It's women. There's definitely a Prince Charming ideal. It's not a movie. There is no right one. There are 6 billion people on the planet — chances are more than one of them will get along with you."

Schefft agrees, but thinks some mates are mismatched.

"I don't think there's one right person and that's it," she said. "But there are people out there who suit you better than others. Don't waste your time on relationships that are bad."

Hill preaches realism when it comes to love, advising against thinking you can change your spouse, encouraging independence and offering a reminder that all relationships have flaws and require hard work. He said there's only one thing that everyone should refuse to settle for under any circumstances: abuse.

And in the end, choosing a partner isn't like scouting out a car, a piece of furniture or a pair of shoes. It's an entirely different kind of search.

"People approach relationships like they're shopping," Stevens said. "We nitpick a lot of times. There's a reason Rapunzel's hair was that long. She was waiting."