Some writing has complex sentence structure. Many times, this is because its authors derived it from drafts that had complex sentence structure already. But I read that writers can combine simpler sentences into more complex ones through sentence combining. Unfortunately, I don't understand how some complex sentences can be represented as simpler ones, especially when the propositions in it are connected by relationships. Because I fail to understand this, I also struggle to see how I can write sentences without attending to their complexity, and then combine them into complex ones. Therefore, I lack the willingness to write. And partially because of this, I do not write.
My question is this: Are sentence complexity and thought complexity always independent, and how can complex sentences which seem irreducible be broken down into simpler ones? If I understand this, I will be more likely to follow an effective writing process, involving ignoring writing style when inventing or drafting, enabling me to write drafts with simple sentences and revise them into drafts with more complex ones.