Writer's Block (it's so bad I couldn't even come up with a better title)

Every time that I write anything the story always begins as the perfect story within my imagination.  Whether it is based on my own life or totally unrelated, it begins as a perfect story and with every sentence I write this perfect story becomes more and more damaged.  I am fine with this; I feel like as a writer my job is to try to do the least amount of damage possible, but some damage is inevitable.  Usually the perfect story consists of totally opposing ideas and situations that cannot exist simultaneously, but in my mind they can.  I never have to choose between them.  It's only when I write them down that I choose.  This semester I haven't been able to.  I think that I have sat comfortably with some of these stories in my head for too long.  Even before summer started, I had the idea for a character based on a real person; this character is the inspiration for both assignments one and two in my creative writing class, and I can't seem to write her at all.  I have seen her as a real person and I keep feeling that to write her would be to ruin her.  I can't write her in a way that does her justice.  In these stories I can only think of fragments; I write notes and ideas, but they don't seem to connect at any point. This post is a downer. Sorry.