That simple piece of dialog tells you about the speaker's insecurity or uncertainty. Perhaps it's more obvious when others speak, but we also catch the timidity in their writing when they use statements such as, "It seems to me" or "I like to think." Or we notice the dogmatism with sentences like this. "If you ever want to succeed you must follow every rule and no deviations. There is only one way to master this topic." The more unsure of themselves they are, the more they go to one extreme or the other.
By contrast, writing with your voice means you trust your knowledge and technique sufficiently to use your own words, your personal style, and present your outlook as your own.
When you write on different subjects, your approach varies, but you're still writing with your voice.
For example, clarity is a primary rule for me. I want readers to understand, so I use a direct approach and as few words as possible. It's my style and my voice. Some have accused me of being a choppy writer and I wouldn't argue.
Or I would write the above paragraph like this: For example, clarity is a paramount concern for me and I strive to enable prospective readers to understand, grasp, and ingest my words through a straightforward, undeviating style, and in so doing I use as few words as necessary to convey my intention and my meaning; after all, I want them to grasp my style and my voice even though some have accused me of being a choppy writer and I wouldn't argue a great deal about their accusation.
In the first paragraph I used 44 words and four sentences; in the latter, 79 words for a single sentence.
Your true writing voice is truly you.