You force yourself to focus and once you do beautiful things happen. I found that when I set a deadline for myself I was able to at least FINISH something. It wasn't necessarily the best song or the best songs, but I got something done. Next time set a limit for yourself.
I forced myself to write a verse melody and chorus melody in an hour. Got it done! Set a deadline for yourself. I think it would even help to have other people involved. Get a buddy and say... " hey i have this song i want to show you, let me show it to you on thursday!"....and you won't actually have a song YET, but now there is another person involved. So you HAVE TO GET IT DONE. bambam pow. DO IT.