The main thing is that you have to ask yourself: what gave you the motivation or inspiration to finish something in the first place? Was it a show you liked to watch? Or maybe an artist you admire?
Whatever the case, look back on that. Try to rekindle that spark of motivation/inspiration. But regardless, please realize that it's not always going to work forever, and that you're going to have to eventually learn how to force it yourself. And that's something that no one but yourself can do.
Just a little penny for thought, since I've been going through something similar for a really long time with my art.