Talk your thoughts instead of writing them. Tell a story, or muse and ponder, out loud – and record yourself doing so. Then play it back.
What metaphors and idioms do you use? Do you have an accent, or use words and phrases that betray your origins? What are you not saying, and why aren’t you saying it? Pay attention to the cadence of your speech, the rhythm of your words. Do you write true to your own voice?
Transcribe the recording verbatim, and then edit the transcription, removing the ums and ers and sidetracks, but preserving the rhythm and your voice. Who knows, maybe you will learn something new about yourself.
By the way, this also works for building fictional characters. Talk aloud as if you are your character. What are they trying to tell you? Are you listening?