Do you start, and inexplicably stop? Let me offer this thought.
The symptoms of the struggle to write are things like staring at a blank page. Not wanting to get up for that 5.30 am writing slot (Eurgh. Whoever thought that was a good idea?). Resistance, showing up in the form of doing anything but anything, cleaning the dishes, the car, the cat, just to avoid your notebook or laptop.
You’re not lazy. The causes of the struggle to write are:
Not being clear why you want to write this book (purpose).
Not knowing who you are writing for (reader).
Not knowing what you need to write (content).
What steps can you take to solve the cause of your struggle?