It's common for people to change at least a little bit for love.

Even Hollywood stars make life modifications that seem to be for their significant others. Brad Pitt became a motorcycle-riding, child-adopting, tattooed philanthropist for Angelina Jolie; Katie Holmes became a stick-thin society woman for Tom Cruise and Jessica Simpson transformed into a brown-haired rocker girl for John Mayer.

But at press time, Simpson's relationship with Mayer is either over or very much on the rocks. So the question bears asking: Should people resist the urge to "morph" and fight to stay true to themselves in a relationship? Or is it normal to want to merge?

Relationship expert Nancy Pina, author of “Goodbye, Mr. Wrong” and founder of yourtruematch.com, said people make big lifestyle changes when marrying or in a serious relationship because they fear being alone or somehow losing their partner.

“They feel lifestyle accommodation and catering to another person’s every need will ensure a lasting relationship," she said.

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But bending over backward for a loved one doesn’t always amount to boundless bliss.

Despite switching styles for every serious sweetheart, Pitt’s love life has lapsed many times. The actor went bohemian in 1990 for Juliette Lewis, smooth and finished in 1996 for Gwyneth Paltrow and calm and cool to marry Jennifer Aniston in 2000.

But since 2005, when he began his romantic rendezvous with humanitarian hottie Angelina Jolie, Pitt has passed on to a philanthropic phase.

According to In Touch magazine, Pitt even has a tattoo of a Buddhist protection prayer on his back in honor of Brangelina's adopted son Maddox, which reportedly matches the one on Angelina’s left shoulder.

Jessica Simpson is another star who altered her lifestyle after falling in love — in her case, with guitarist-pop singer Mayer.

“There’s nothing worse than trying to look like you’re a rocker when you’re not,” she told Australia’s WHO Magazine in 2005. “I like glamour.”

But Simpson revamped from bubbly blonde to boho brunette once she started dating Mayer ... and has gone blonde again since reports of a break-up (she says the new locks are for a role).

While dating Mayer, Simpson also went from go-getter to groupie, putting her own singing on the side to be with her beau on his world tour earlier this year.

This too could have been a sign of impending doom.

Marianne Matheson, a 35-year-old Los Angeles movie producer, regrets giving up her job making films when she tied the knot 10 years ago.

“My ex-husband was a prolific businessman and wanted me to travel with him as well as cook, clean and care for the kids,” said Matheson. “I wanted so badly to be happy and for it to all work out like that, but I missed my old life. We divorced two years ago and I’m back to where I started.”

The split comes as no surprise to relationship experts.

“It is not fair nor healthy for the longevity of the relationship for one person to completely give up their career, especially if that is not what that person wants,” said Pina. “Simply because one half earns more money than the other does not mean he/she can dictate the dreams and desires of their partner.”

Couples also often butt heads over which partner should convert his or her religious faith in the name of nuptials.

Since marrying Tom Cruise in 2006, Katie Holmes not only has become more reticent with the media, much thinner and far more fashionably dressed in more classically conservative clothes, she also has canned Catholicism and stepped into Scientology to suit her husband’s style.

Australia resident Reuben Locke, 27, also made a mammoth move for love from a Baptist upbringing to the beliefs of Islam.

“You can’t help who you fall in love with,” he said. “The woman of my dreams is Islamic so I really had no choice. I used to get upset and miss the things in my old life, but you learn to move past it.”

However, conversion is an individual choice, and it should never be imposed, said Sloane Veshinski, a Hollywood-based marriage and family therapist.

“For the relationship to remain strong, the person making these changes must do it because they want to and chose to and not because they were coerced,” she advised.

But how many changes does a person really need to make a relationship work?

“It is necessary to make minor accommodations for the other person,” said Veshinski. “But relationships should be fair and balanced with each partner having an equal say.”

So perhaps the more a person changes to befit their beloved, the more likely it is the fervor will fizzle.

“Too many transformations made for the wrong reasons is quite often the downfall of a relationship,” Pina said. “If fear is driving any change, resentment and anger will build internally. When these negative emotions are buried alive inside of us, they poison and distort our view of the world.”

Matheson agrees, saying her once happy marriage was hampered by the pressure to change.

“If I hadn’t given in to everything my husband wanted things may have worked out,” she said. “But it was doomed from the start. I just couldn’t cope with living my life for somebody else.”

If change is carried out in a caring and compromising manner, the bond will actually benefit, experts say. But love will only last if both partners accept one another for who they really are deep down.

“When somebody tries to change who they are for a person or relationship, those changes are not usually long-term and thus they are presenting a false front,” said Veshinski.

“But true love is true because the other person loves you despite your little idiosyncrasies and interesting habits. The relationship should be a starting point for both individuals to grow together both spiritually and emotionally.”

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