This might sound like a no-brainer, but you have to literally set aside time to write.
This might sound like a no-brainer, but you have to literally set aside time to write. Just deciding you’ll write Mondays and Wednesdays will probably not result in you actually writing  on Mondays and Wednesdays. In all likelihood, you’re already filling that time with something else, and that’s what you’re used to, so it’s not likely to change.