The more transformational we want our work to be, the more delusional we are at the outset of it. It's not just a fact, it's a necessity.
How else will you sleep at night, when you know the majority of startups fail? If you were to believe the statistic reflects your chances, you wouldn't go very far trying to be different.
What matters is whether you have enough people around you to entertain your delusion and to expand it. Both roles are important. Those who entertain your delusion, such as family and friends, provide you support and perspective. They entertain your beliefs because they believe in you. Those who expand your delusion, such as cofounders or early users, make it more real. You are intimate from the get go (or at least, you have the opportunity to be), because you both see a value that's waiting to be born.
And yet, delusion can be your greatest foe when you make it personal. When you seek to prove anything: that others were wrong, that you could in fact do it. That meant part of you does believe you are misguided, or that you can't do it, and so you fear that part is right. So you may put on horse-blinders, to shield you from discouragement, and those horse-blinders will keep you from making your delusion more real, from turning a potential into a value for others.
Keeping it humble
The communicable reality, as it is, hardly contains that value you care for. If you feel connected to someone when you talk about your startup project, it means you both share something that cannot be communicated quite yet. Charisma, to some degree, involves eliciting that sense of connection with the people around you.
Now, when you feel that connection, do you feel vindicated or expanded in your vision? Do you think the other is more intelligent because they get you (so your delusion is about your ego), or do you feel like you just found a partner to explore new thoughts with (so your delusion is actually shared)?
A large part of your success will reside in whether you can keep the delusion humble. Whether it can change depending on what you're learning, and whether no-one's sense of identity hinges on it.