This has happened to me many times. I write write and write and then I loose track. I go blank and I don't know where to start. I stop writing for few days. I sit alone at night, read what I have written and try to connect. If I still am not sure what to write, I just leave it and start a new one. For me, it has happened, that I haven't got any ideas so I leave it. And something happens that makes me connect to my story again. Well it could be a conversion i overhear in a restaurant, it could be people I see or just about anything.