I agree, my writing is very much influenced by a variety of things like many others. Its a reflection of my mood, for instance am I tired or wide awake. Each of these feelings reflect by the words in which I choose to write. Also my audience is a big influence on how I write. Not only in the form of professional vs non-professional but also how I feel about the audience in which I am writing too.
However, over all I agree with your point that over time writing will help you learn more about yourself and the type of feelings or things that influence your writing!
When I started writing for an audience it was professionally for non-native English speakers which was both challenging and rewarding. It forced me to simplify a lot which is a good thing. It limited the range quite a lot though and I feel much freer at Steemit even though most readers are likely non-natives.