Finding the voice

Hey guys,
I thought I would share one of the most difficult things that I have run across as a writer. Finding your voice can be a very difficult task depending on what you choose to write about. To obtain a masters degree in American history it requires countless research and writing assignments. I was quite comfortable writing this way I would get in trouble or would lose points when I strayed to a narrative style too much. Writing books for public consumption you want to bring that narrative voice out but also keep the facts and the historical record intact and that's the hard part. I've read through my first two books and at times I felt I was a little too flowing with my narrative and then at other times I felt that I was too straightforward with just historical facts. The difficult part and what I am working on is finding a good voice that is a happy medium between the two. What do you all struggle with when writing? I would love to read some comments
take care