How to Cancel a Friend Request You Sent on Facebook
Before you connect with another Facebook user, the social networking site requires that you send a request for friendship. Once you send the request, the other Facebook user has an opportunity to review it and either accept or deny a friendship with you. If, after sending a friend request, you change your mind, canceling the request is easy. With just click, the friend request will be revoked.
Point your browser to the profile of the person to whom you previously sent a friend request. Either use the search engine at the top of the Facebook screen to search for the person by name or click on her name on a mutual friend's profile.
Click the "Cancel Friend Request" link just beneath the Facebook user's profile picture.
Request friendship from the person again in the future by returning to her profile and clicking the "Add as Friend" button just to the right of her name.