Separation Anxiety

As a journalist I have been taught to delve into a story to find the nitty gritty facts that might otherwise go unnoticed. And yet at the same time I am told to keep my distance from stories and not get to close because I don't want them to be biased. So my question is: Where is the line??
Isn't all journalism biased to some extent? I mean, it has to be.
I report for BYU Eleven News. When I go to find a story, I am looking for something that the public will find interesting and want to know. But I can't possible know what the public (namely my viewers) are going to want to see. I am biased in that I am the one who is choosing what to do a story on. Obviously I'm going to find stories that interest me to some extent. Recently I have found stories that I am passionate about. Is that wrong? If I find a story that I am truly passionate about won't that make the story better? Won't it make it more interesting to watch because my passion will force me to tell it in a way that people can relate to?
Or am I ruining the story? I don't know how to find the line.
Is my passion for the stories I am telling skewing the truth? Think of Anderson Cooper. When he reported on Hurricane Katrina he was very passionate about it.I think that his passion helped him to find elements of the story that people wanted to hear about. Isn't there a way to incorporate your passion for the better? As long as your staying objective with the facts and not blatantly putting your opinion in your story, does it matter?
One of my favorite stories that I did was on a campaign project called Beauty Redefined. Their goal was to teach women how the media is skewing what beauty really is. I think that part of the reason that it was my favorite story was because I became an advocate for their cause. Now the story didn't air so I can look at it from another point of view. Was my story skewed because I was an advocate for the cause? I think in this case, the answer is yes.
I didn't talk to a professional to see if what this program was promoting was based on fact or opinion. I instantly believed what Lexie (the co-founder I interviewed) had to say and I even stayed after the interview to chat with her. Little did I know then, that was a big No-No in the professional news world.
Lucky for me I am just learning and it is time to make my mistakes now. But I still need help finding that line between getting good facts and being a full out advocate for the story. Maybe this is something that people can't teach me. Maybe I have to figure this out myself with trial and error. I don't want to have a lawsuit on my hands in the future for being seen having a friendship with people I use as sources. If I am going to be a reporter, I am going to do it the right way. I guess its a good thing I'm in school so I can figure out what the right way is.