Writing a book is good for you. It clarifies your thinking and it’s generous as well. You might not publish it professionally, but sharing it with people you want to teach and lead is a useful practice.
The first draft can be challenging. We’re facing a blank page, trying to find our “voice” and it often ends up sounding stilted, fake or just plain boring.
Perhaps this alternative might help:
Get a cheap digital tape recorder. Go on a walk with someone you want to teach about your topic of expertise. Spend half an hour explaining, in the most cogent way you can, person to person, what they might learn from you.
When you’re simply talking and walking, teaching from experience and anecdote, your best voice arrives.
Go ahead and transcribe the recording and your first draft is done.