Doubt

I am planning a long run tomorrow. 18 miles. Alone.
It will not be my first time.
I've had it on the calendar for months.
I am well-prepared, having run 16 last week.
And, yet...
I doubt.
It doesn't seem possible.
I can't do it. Not alone.
My tummy is anxious, my breathing is shallow, my legs are twitching.
I hope I wake up on time. I hope my tummy settles down. I hope it goes
as well as every other long run.