I struggled with the same problem, the 8 hours of solid productivity a day is a killer after working remotely during several days. My solution for that is the Pomodoro technique, I wrote an article about that, hope you find it useful: https://medium.com/@marcochvez/how-i-get-my-workday-done-in-...
> I have been working remotely for two years and I struggled setting my own schedule. Sometimes I ended my day feeling unproductive or wondering how I was spending my time without being aware of what I accomplished.
> One solution to my problem is the Pomodoro technique, which is a method to break down work into intervals of 25 minutes.
> A study (that helped me to figure out that question) reveals that the average worker is only productive for 2 hours and 53 minutes per day, the remaining time is spent in activities unrelated to work (checking social media, reading news, discussing out of work activities with colleagues, etc.).
> Taking the 2 hours and 53 minutes as base, that gives us approximately 7 intervals of 25 minutes, although in practice I’m doing 8 to 10 intervals. This could vary per person and the type of work, but at least we could consider 7 as the minimum. Also I found out that writing down consciously what I’m going to do in my next interval helps me to create peace of mind about my productive time, because at the end of each day I finish with a task history that justifies my work.
> After a few months using a spreadsheet and a Pomodoro timer I was looking for a solution to integrate these tools seamlessly, Despite trying different and complex Pomodoro apps I decided to create a simple and minimalistic solution named Work & Flow