Dear Doubt,

It's understandable that you have risen.  You are at a stage in your journey that is untrodden by you.  This is a path you have not walked, yet.  The uncertainty that you can do it, is normal dear one.  You see where you need to be but the path seems too long.  See the first step, then the next, learn from each move.  Move forward, build the strength you need to keep moving.  Rest when you need to and get up again.  This is normal dear one.  Do not fear, this is growth.