You buy her gifts, help her study for exams, walk her dog when she is away and drive her to the mall when she needs a lift. But -- when you need a favor or a shoulder to cry on -- poof, she is gone. If you've let someone hold all the power in a friendship, to the point that you keep giving and she keeps taking, it's time to gather some self-respect and start saying "No."

Learn to Say "No"

If you lack assertiveness, you probably have a hard time saying no when others ask you to do things, says author Shay Youngblood, in the Oprah.com article, "Stop Being a Pushover!" You might feel as though you need to be a "good" friend and help out when asked. Unfortunately, bending over backwards for a friend who doesn't appreciate your action only gives her the power to keep taking from you. Stand your ground and use simple phrases like, "Sorry, I can't this time," or "Sorry I have plans." It is also okay to let a friend know you need time to make a decision by saying, "I'll get back to you."

Treat Yourself With Respect

If you don't treat yourself with respect, others will not treat you well either. On the other hand, if you have clear boundaries and refuse to budge, you will attract the respect of your friend, writes communications professor Preston Ni, in the Psychology Today article, "Are You Too Nice? 7 Ways to Gain Appreciation and Respect." For example, if a friend puts you down or calls you names, calmly tell him that you will not be treated badly and that you expect more. If he continues to treat you disrespectfully, cut off contact and say, "I will not be treated this way. I deserve more respect." When you stand firm, you will eventually regain power in the friendship -- or go your separate ways.

Stop Letting Go of the Lead

Your friend says she likes purple eyeshadow -- you agree. Your friend prefers ice skating over roller blading -- so you do as well. Every choice that is made by the two of you goes the way of your friend's preferences, in essence rendering you powerless in the friendship. If you've been letting your friend make all of the decisions, it is time to step up and start stating your wishes and sharing your opinions. Though it might feel scary at first, going along with everything she wants will only leave you feeling frustrated and resentful.

Be Less Available

Sometimes a friendship can become imbalanced because one of you is much more available than the other. If you are always the one making plans, keeping in touch and offering to tailor your schedule to your friend's, it might be time to take a step back. Let your friend do a bit of the chasing and the planning, and she will become more invested in the relationship. Shifting the power imbalance in this way takes time, but if you are consistently unavailable, eventually she will need to track you down.