Many of us writers have assumptions that hold us back.
For instance, do you assume there’s a specific limit to the number of words you can write in one session? What if you experimented with beating that limit? (I did that some years ago and it led to a real breakthrough.)
Do you assume that you have to write everything in order? What if you tried writing the scenes for which you already have a strong feeling first?
Do you assume that publishing is all about who you know, not what you write? When you read stories about people getting their first novel published, do they actually support that assumption?
Do you assume that experts who could help you with answers to your research questions for your book are too busy or would turn you down because you've not had anything published before? In fact I've found people like that very helpful, even at the beginning of my writing career.
The point is that you may be constructing limits for your writing that have no basis in fact and are hurting you. Take a few minutes to consider your assumptions about writing. Are they true? Are they helping you or holding you back? What alternatives might serve you better?
(I assume that you'd benefit from the advice in my book, "Your Writing Coach" published by Nicholas Brealey and available from Amazon and other book sellers.)