Thanks to the Internet, nearly anyone can share thoughts and be heard. Even when I post something on my personal blog (that hardly anyone reads), I still see hundreds of visitors each month. My voice is heard by a small audience.
As an online freelancer, though, you have the potential to reach a wider pool of people. My words have reached hundreds of thousands of people over the years. However, just because you are providing the words, it doesn't mean that you should always use your own voice.
When you are writing for pay, the reality is that there are times that your voice isn't wanted. This is especially true when you are ghostwriting. When you ghostwrite, you really are supposed to be someone else. You give them a voice; your voice isn't the focus.
However, there are times when your byline shows up on something that you don't think really “feels” like you. This might be the result of a client wanting specific things shared in the article, or because there is a style guide to follow. Sometimes, the style you follow doesn't really complement your own voice — your “true” voice.
The reality, though, is that none of that matters. You might want to write in your own voice, but when you are getting paid, you need to write in the voice that the client wants. If this is the case, save your own voice for your personal writing and your own blog. At some point, you might get paid for who you are, but until you are, the job is to make the client happy (at least if you want to get paid).