Agree with David Heinemeier Hansson about putting the blinders on in the beginning and guarding motivation (hadn’t heard that term before but its beautiful).
I remember Sara Blakely saying something similar where she didn’t share what she was working on for one year, even with her friends and family .
The reasons to guard motivation, in my experience are:
1. Ideas and motivation are fragile. It has nothing to do with founder mental toughness
2. You will most likely seek feedback from well meaning people who are not your actual users
3. You will give up before you talk to your real users
In the end, if it was fun, who cares anyway? 🙂