After finishing my journalism degree I ended up as a technical writer all by accident.
As a professional writer that worked on manuals between 300 - 600 pages long within 3 months I had to find a way to get through the days where writing was just not happening.
So I figured out a series of other productive tasks that needed doing that contributed to the job getting finished.
Other days I would just push myself to write something. It didn't have to be brilliant or even spot on, it just had to start to be there. Points could be written but not filled out.
Just as long as something was getting on paper then I found it easier to edit it a few hours later or in the coming days.
Then it became the practising that pulled me through the slow writing days. I learned at university that you couldn't call yourself a journalist until you had written 6 stories a day, 6 days a week for 6 months.
The same applies to any writing; professional writing, journalism, tech writing, blogging, copy writing, speech writing etc.
So when you have writers block don't dwell on it. It will pass and you can start writing to get something on the page as it's much easier to edit to create something good. It is the doing that matters.
Just be kind to yourself and remember, classic books like "The French Lieutenant's Woman" were written and rewritten over ten years (although writing on the same thing for 10 years would personally drive me nuts!).
All the best,
Belinda