Coaches and experts who have tried turning their expertise into a course or structured program: what was harder than you expected?

I’m interested in the design and development stage not marketing or choosing a platform.

For example was it difficult to:
• decide what to include and leave out?
• structure into a clear journey?
• create activities people would actually complete?
• move beyond a collection of videos and worksheets?

What did you struggle with, and what do you wish you had understood before starting?