Friendships are among the most important things in life. Some people assume that the longer the duration of the friendship, the better the friend. But that's not necessarily true.

Friendships come in all shapes and sizes, "and some don't have a very long shelf life," says Sandy Sheehy, author of Connecting: The Enduring Power of Female Friendship. There is a point when you hold on too long, allowing unhealthy connections to continue.

Breaking Up Is Hard to Do

It can be hard to admit it's time to say goodbye to a friend, even when her behavior warrants it, as Cindy Gallagher, of Maryland, learned first-hand. Her long-time friend, Helen, balked at any attempt Cindy made for independence, such as when Cindy's parents visited and she didn't tell Helen. And Helen fumed when Cindy's now-husband bought her engagement ring without consulting Helen first. Helen confronted Cindy, telling her she was getting "uppity."

"She had me in tears at first because I was so shocked and she was so angry," Cindy recalls.

The two tried to patch things up, but the clincher came when Helen bad-mouthed Cindy at her wedding reception.

"I realized this woman is just not a friend of mine, not a true friend," she says. "After that, I just made excuses not to see her…and she quickly got the message."

Knowing the Signals

While betrayal or seemingly deliberate attempts to be hurtful are clear signs it's time to say goodbye, sometimes the signal of the end of a friendship isn't obvious. You may sense a gradual distancing or feel unstimulated by the other person, or the relationship may just require more care and maintenance than you're prepared to give.

Doing What's Right for You

No matter the reason, ending a friendship can be very difficult for many women.

"The idea of having to end a friendship is something women kind of chicken out at," Sheehy says. It may be because of the desire to avoid conflict or the wish to be seen as "nice" and not hurt the other person.

"Women will do a lot of things that aren't in their own self-interest, that aren't good for them, to stay in relationships with people they care about," Sheehy adds.

But by allowing unhealthy or unfulfilling friendships to continue, you could be sacrificing your own well-being. If the relationship has stagnated, then you're spending your scarcest resource time on something that doesn't add to your life. And if the friendship is downright unhealthy, as Cindy's was, you may even risk your emotional health and happiness.

"A woman should not spend her valuable personal time in a relationship unless it enhances her life, helps her be the best person she can be, encourages her to follow her dreams, [and] supports her in her struggles," says Marilyn Sorensen, PhD, a Portland, Oregon-based clinical psychologist and author of Breaking the Chain of Low Self-Esteem.

Ending It Gracefully

Ending a relationship tactfully can be challenging.. It's often difficult to get the space you need without hurting the other person's feelings, but it can be done.

The easiest approach is to simply let things cool. Don't phone as frequently, don't agree to get together, and don't give excuses, says Florence Isaacs, author of Toxic Friends/True Friends: How Your Friends Can Make or Break Your Health, Happiness, Family, and Career. Giving excuses allows the other person an opportunity to overcome your refusal. For example, she'll answer your "Oh, I don't have a sitter that night" with "That's okay, my sister volunteered to watch the kids".

By being less active in the friendship, you gain emotional and physical distance. This is a good technique, says Sheehy, if you still want to be friends with the person but want to lessen the intensity of the relationship, or if you really don't have the time at the moment to maintain the friendship but would like to pick up again down the road.

The drawback of the indirect method, though, is that it isn't the most honest approach and may leave the other person confused about what's happening, says Dr. Sorensen. In some cases, the friend won't "get it" and will continue to pursue the relationship even as you're trying to back off.

Straight Shooting

If your message isn't getting through or if your friend's behavior has been so hurtful that you need to end things completely and quickly, take the direct route.

"Assertively talk to the person about your differences and why you would like to end the relationship," says Dr. Sorensen. "Assertiveness is usually the most desirable way to handle conflict because it is honest and lets both parties know where they stand."

If you choose the direct approach, speak in "I" statements. Focus on how you feel and what you want, rather than on the perceived wrongs of the other person, says Isaacs. By not accusing or blaming and by stating your position clearly and calmly, you'll run the best chance of ending things as positively as possible.

The decision to terminate any relationship should come only after you've concluded that the connection is unsalvageable and you're better off without that person in your life. Remind yourself that ending things is the best decision in the long run, and that doing so will make room in your life for more positive, nurturing people.

Dr. Sorensen puts it this way: "Having someone with whom to share your successes and failures, your hopes and dreams, is a priceless thing. It's a choice we have. Choose wisely."