There will always be doubts.
Doubts about whether or not this will work, or if you’ll be rejected, or if people will like it.
But if there were never any doubts, then there would never be any opportunities either, because everyone would have already solved every problem, as there would be no hesitation.
If you don’t have any doubts then you are definitely not on the right track.
If you’re facing doubt, then you might be onto something worthwhile.