Hi James!
What I have done when everything around me seems to be going wrong, when I compare myself to others and feel downturned, when I feel like quitting, is to just keep going.
Keep publishing. Show yourself this is not the end. Show yourself there are more ideas to be explored, people to help, people to entertain.
As to how you fell there, that is a very tough one. I still don't know how I fell in this de-motivation hole myself.
Truth is, as with anything, the excitement for something new often fades away with time. This happens with anything, and I guess this happened to my writing as well.
I started questioning myself, whether I was good enough or not. But I just kept going. So should you.
Keep it up, I want to see you rise.