Doubt is an inevitable part of life.
These things may give us reason to say “no“; to back down or step away.  But they are so much more.
They are the sign of an opportunity we wouldn’t generally be presented with.  They are the gateways to something greater, that often leave marks behind (Yes, sometimes these marks are scars, but they can also be something wonderful).
So don’t take doubt as a warning sign you must heed.
Take it as a possibility to adventure.