A writer’s voice is authentically yours, but it isn’t a fixed and final Holy Grail version you go on a quest to discover and never deviate from. Voice can evolve or shift, not just over time but between different projects.
Why? Because voice has more to do with the writer’s ease in expression while writing.
Secondary school English teachers urge students to “write the way you talk.” This is an imperfect, misunderstood way of using your writing voice, but it does put you at the right starting line in the race.
Do you feel “in flow” while you write? Are the thoughts and words coming easily, pen furiously scribbling or fingers flying over the keyboard?
And when you settle down to revise, do you have to spend little to no time changing phrasing, diction, syntax, and tone?
Do you enjoy re-reading your work, even if you are frustrated that it isn’t living up to your goals and intentions (because it needs revision ^^^)? Do you recognize your words as something you wrote?
If your answers are all "yes," you have found your voice.