Hi Zeroh.
I have a postie note on my computer:
Don't neglect your writing,
But do not force it either
Let it write itself!
Sometimes when I am wanting to write, but can't seem to get in the "creative zone" to write something I feel is "up to par" then I write some ideas down beneath the text...incomplete sentences, one word ideas as to where I may want to take my project. Then later I can work these ideas into completed format.
Often times the ideas spark the "mood" and I am off and flying with writing again. Other times these ideas may spark something totally different than what I was trying to work on...which is why I have fifteen books started in my computer. Depends what I feel like working on is what I let flow from my fingertips.
Never have I experienced writer's block. It just does not exist for me. Rather, I find a lack of time my biggest hurdle.
good luck and never give up...you will accomplish your goals.
If you're writing a maths book, please do this! Make it flow through. I was always rubbish at maths, and the books confused me. They always wrote in TEXT rather than showing examples so I never knew how to put something. PLEASE show examples. Preferably in bright colours to stand out! Good luck!