It sounds like you have started lots of things and can't see the end. You might try focusing on finishing one thing. If on a layout, finish an area of it, enough to do some switching or take some pictures. Finish a kit and get it on the layout and feel the joy of accomplishment. I have done all these things when feeling down.
Another thing I noticed when I built a couple of layouts early on. They were loops with some sidings here and there and I think one had double track. However, once I got them sort of along and running, my intereset dwindled. Without knowing it, I realized I was thinking "what now". After that I attended an NMRA convention and met some guys doing operations and got invited to some sessions. It was a whole new world for me. I came up with a method to route freight cars to the sidings on my layout, and I really started enjoying it. I got to the point where I hardly ever used the loop. When I have about 6-8 industries or switching sites (2 were interchanges), and a dozen or so freight cars, it would take me about an hour real time to pick up all the cars from the industries and put them on the interchanges and pull the cars from the interchanges and put them in the industries. That would be a fun adventure. And it usually led to some maintenance project or new piece of rolling stock I wanted so it fertilized my interest.
