"We begin forming attachment to our parents the moment we're born," Dr. Anna Hiatt Nicholaides, Psy.D., licensed clinical psychologist who specializes in relationships, tells Bustle. "These same attachments occur with our significant others when we begin to be romantic." These are called "romantic attachments," and they're just as strong and powerful as the attachments you made early on in your life.

As Nicholaides says, "This is why our connection to romantic partners feel so life-and-death." When a relationship is over, this attachment can make you crave the stability you once had. If your ex made you feel loved and desired, you may hold on to those feelings and keep looking for it even you decide to just stay friends.

According to Nicholaides, the best way to form a friendship with an ex is to find another partner you feel attached to. "The reason this works is because you've transferred your romantic attachment to another person," she says. "This doesn't mean you won't feel residual feelings of possessiveness or jealousy, but they won't be nearly as strong." Going to a therapist can also help you sort out any attachment-related issues.

Sometimes it's just too soon. A study published in The Journal of Positive Psychology found that it takes at least three months for someone to get over an ex. Depending on the length of your relationship and how attached you are, it can take even longer. If you're still hurting from the breakup, maintaining a friendship is going to be really tough.

"Sometimes you need to take time to heal," Dr. Sanam Hafeez, neuropsychologist who specializes in helping individuals work through relationship issues, tells Bustle. "Even if a relationship ends mutually and on good terms, the turmoil that resulted in the break up can be fresh months and even years after."

Ending a relationship is always tough. While staying friends may seem like a good way to keep your ex in your life, it's going to be difficult if you still have feelings for them. As Hafeez says, "It's going to be hard to be friends with them without it being torture to you and possibly uncomfortable for them." So if you want to stay friends, you need to think about what you actually hope to gain from doing so.

A 2011 study published in the journal Personal Relationships found that your motivation can determine whether you can have a successful friendship with your ex or not. There are four major reasons behind why people choose to stay friends: security, practical reasons, civility, and unresolved attraction. People who still had "unresolved romantic desires" were less likely to feel secure and happy in a friendship with their ex, the study found. They were more likely to feel depressed, jealous, and brokenhearted. According to the researchers, people who stayed friends in order to be civil or because of practical reasons were more likely to be successful in their friendships.

There's nothing wrong with wanting to keep someone who's important to you in your life. According to Hafeez, people who can stay friends are those who are honest with themselves about why the relationship didn't work out, have nothing but positive feelings towards their ex, and may have already moved on to someone else.

Staying friends with an ex isn't for everyone. If you're still in love and still attached, you may need to think about whether a friendship is really a good idea. Sometimes it can be more trouble than it's worth.