According to a strict definition, voice has two meanings as it concerns creative writers:
'Voice is the author's style, the quality that makes his or her writing unique, and which conveys the author's attitude, personality, and character; or
Voice is the characteristic speech and thought patterns of a first-person narrator; a persona. Because voice has so much to do with the reader's experience of a work of literature, it is one of the most important elements of a piece of writing.'
I think it's more about finding out who YOU are. How YOUR reactions to life are different from everyone else's. What things YOU have to say which are different from everyone else.
How many times have ten writers sat in a room with the same writing prompt, and have produced ten incredibly different stories.
Unfortunately, for most writers you need a certain level of confidence and self awareness to speak in your own voice.
I've been thinking about some of my favourite writers. And I think they are good, not just because they write a great deal, but because they care. They understand a little bit about life, and they try to pass it on. As we live our lives, we begin to discover what helps in life and what hurts, and our characters act this out dramatically. This writing from the heart and the head is what produces a unique voice.