Use tools and systems to organize your day

Have a file system for this and next month, where you put in stuff that you'll have to get back to.

Block your time. Make inviolate appointments with yourself.
Block a few hours in the morning for writing. Block time weeks and months in advance.

Minimize unplanned activity. For a task, determine in advance how long it takes and set a time for its completion.
By reducing unscheduled time and unplanned activity, you automatically reduce waste. If you can't tell where your time goes, you're unproductive.

Profit from "Odd-Lot" Time.
When you have to wait anywhere (airport, road traffic, doctor, etc.), have learning material with you so that time doesn't waste.

Live Off-Peak.
Avoid things like going shopping the day before a public holiday, etc.