Delusionists vs Imposters
In startups, being delusional is a valued trait. People often speak of a great founder's ability to stay focused on their vision despite the outside doubt. To push on when everybody else thinks their idea is bad or tried.
When shouldering this doubt head-on as a solo builder, it's even more important to hold your idea in diamond hands. There is no cofounder or wider team to lean on when self-doubt creeps in.
For someone that has had self-doubt creep in, and stay a while, I've noticed it's similarity to the admirable trait of delusion.
Founder delusion is when everyone on the outside is invalidating you but you push ahead anyway.
Imposter syndrome is when everyone on the outside is offering you validation but you submit to self-doubt anyway.
Founder delusion and Imposter syndrome are opposite vectors. Whichever has a larger magnitude will win out. The resultant vector is what the world will see and what will propel your project to it's fate.