It is normal to assume that seeing a finished text (be it a book, a post or something on instagram) in which the author focused on writing and achieved his inspiration. We forgot that there was a process behind, I need several polishes to stay as it was, the first draft, the reissues (more than writing you have to rewrite), the editing stage and finally the publication.
One of the obstacles of literature is to ignore the process. Writing is a messy process. That is why it is important to understand and accept the processes and not to mythologize them.
It all starts with a notebook and that is why it is so important to document everything for future texts.
If you think this is impractical, click here to write in a travel notebook.