I think a beginner writer's voice goes through three basic phases:
1) the initial natural crude voice
2) attempts to write 'correctly' which make the voice sound unnatural
3) integration of new knowledge and skills, and once more writing in a natural voice, but smoothly, and with more control
It's only natural to feel some panic about 'losing authenticity' while in point 2, but the payoff is worth it, IMO. While in point 1, the amateur author can write any scene in the only way they can, and victory is 'the scene not falling apart', while by point 3 they are capable of writing a scene in various different ways, depending on the needs of the story.
If one is a rare raw talent (and very, very lucky), something written at point 1 can already become a hit. If one hits the sweet spot while at the unnatural style, and becomes a hit with it, one may be forced to write unnatural stuff forevermore or lose the audience
If one makes a name with the sophisticated natural style from point 3, I think that's, among other things, a very good balm against writer's fatigue, which has been discussed in other threads. When one is writing in one's developed natural style, it stands to reason that it drains one's resources way less than the midway unnatural style. IMO.