Dealing with the fine line....

Lately, I have been learning how to deal with the difference of a friend in the workplace and business. This is something that I have been having a really hard time adjusting to with a few people. I really admire and respect the women that I work with, but it has really been hard trying to make the appropriate adjustments that are necessary for me to make it. I feel like I am disappointing people than I really care a lot about. I want to make sure that I make them proud but I feel like I am drowning in disapproval. I can't believe that I have made so many mistakes. I have really made an effort to do well but I still feel like I am failing my superiors. How do you tell the person that I want to impress that I am depressed that I can not make her happy? Its a really fine line that I wish I had the answers to. I want to be a professionally, successful business woman but it has really been hard. My feelings aren't hurt but I don't want people to give up on me because I am a friend or because they feel sorry for me or they feel as if I am not good enough. My shortcomings have made me into a person that I am not happy with.  The more that I come to realization that I am unsuccessful, the more I feel weak and useless. How do you tell someone who can see all the potential and ability in you that you are starting to doubt yourself? How do you deal with the fact that no matter how much you want them to see you as a successful person, you are still can't see yourself but as a cancer patient and a failure? I want so desperately to be the best, however I haven't been able to see past all the things that I can't be. Well I know that we all have those feelings but I have really don't know why it seems to make me feel so DEPRESSED!! I have been depressed lately, which has made me a horrible person to be around.