Doubts, uncertainty, rejection, feelings of inadequacy come attached to every idea.
And the answer, of course, is not to stop having ideas, developing them, sharing them, advocating for them. The answer is getting comfortable with the uncomfortable, accepting that having ideas is but the first step in a long process that could, and actually most of the times will get you nowhere.
When you are ready for that, you might even end up somewhere. It is worth trying.