Once a cheater, always a cheater. We've all heard this adage before, but is it true? When a relationship starts as an affair, one or both parties may have serious issues with fidelity and trusting them to stick with you for the long haul could prove to be a losing game. When you're caught up in the heat of an affair, you may be so excited about your new partner that you fail to see the bigger picture. If he cheated on his wife, what makes you think he won't eventually do the same thing to you? If you were the one who cheated, you may repeat the same mistakes with your new partner.

If you and your partner are trying to turn an affair into a relationship, you have a rough road ahead of you. It's crucial that you are both honest and upfront about why you cheated in the first place. Many people think that affairs are just about sex, but more often than not, there's something deeper at work. If you or your partner is a thrill seeker, then there is a greater chance that there may be another infidelity down the line when the excitement of this new relationship starts to wear off. If you have trouble communicating your needs to your partner and resort to an affair as a way to escape or self-sabotage, there is still the risk of this happening again. Only when two people are clear about what made them stray and have worked toward changing the way they behave in relation to their partner is there any hope that the new relationship will not be doomed to suffer the same fate as the last one.

If you got together with your man while he was still in his previous marriage or relationship, you have to ask yourself if you can really trust him. Is this someone who has the ability to stay committed to one woman for a long period of time? Was he going to leave his wife regardless of his new relationship with you, or is he the type that's always looking for the next hot thing?

Sometimes leaving a marriage and jumping into a new relationship signals a fear of being alone. Ask yourself if your new relationship is based on mutual understanding and trust or if was simply the catalyst for you to get out of a bad relationship. Many times relationships that began as affairs are doomed, not only because of trust issues but because the parties involved haven't done the work they need to do on themselves. At the end of the day, there may be a new face on the pillow next to you, but you are still alone with your same old issues.

People have affairs in part because the grass is greener on the other side. Once the adrenaline rush that comes with sneaking around and having illicit sex wears off, you may find that you are paired with someone who you aren't all that compatible with in the long haul. "Typically, people enter an affair because they're unhappy with their own relationship," says Dr. Yvonne K. Fulbright, author of "The Better Sex Guide to Extraordinary Lovemaking." "While sexual gratification can be a motive, it's typically more emotionally driven for both men and women. They're not getting something in their relationship, so they're seeking it with someone else and aren't necessarily into the person but rather the attention and feelings of being desired."

Fulbright says that a relationship that started as an affair can work -- but it's the exception and not the rule.

"Every now and then, an affair is a matter of two star-crossed lovers finally finding each other. They were never the 'perfect' match with their spouses or exes and everything works out despite the upheaval of breaking up, divorcing and pulling families apart."

Mira (not her real name) had been married to the same man for 14 years when she found herself falling in love with her yoga instructor. After developing a strong friendship and admitting their feelings to one another, the pair told both their spouses that they didn't want to be married anymore. Mira sold her house and moved to another town, even as her new partner was still living with his wife. "I knew that even if he didn't leave her, I was never going back to my husband. I was out. And I was happy about it," she says. Mira says that she didn't sleep with her new love until after her husband had moved out. She and her new boyfriend faced numerous court battles over money and custody of their children and finally wed in a private ceremony she describes as magical. "We are totally in love despite all of the challenges we have gone through. While we knew we would be judged by many, we also knew we were meant to be!" she says.

An affair is not the ideal beginning to any relationship but if you are honest with one another and willing to face the many obstacles that are sure to arise, it just might work.

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Written by Ronnie Koenig for AOL Health