Not knowing is the normal constant state. For most decisions in life, you will not have a full context of knowledge – even if the evidence is overwhelmingly conclusive to be sure in your decision.
Data that disproves what you thought to be true can create doubt in your idea.
Such data can come from research, from experts, and from your experience in implementing your idea.
Doubt based on knowledge is more reliable, and you need to reexamine your assumptions.
Doubt based on lack of knowledge is baseless and damaging. It cannot help you decide and only exert a bad influence on you.
Not knowing should not cause you to doubt. Knowledge should.
It is all hypothetical unless the following is true for you:
1. You fully understand your idea and based on that, you are confident and committed.
2. You are actively implementing your idea.