If I'm stuck on a particular story, I typically will try and get into other stories that I'm working on. Sometimes just shifting gears and moving to other characters in other places is enough to nudge that block out of the way. If the block is a bigger one and I can't get into any of my stories, I typically focus on sending out more submissions to publications or work on rewrites of stories already completed.
Sometimes it works and sometimes it doesn't. When it does it's like a sweet release and when it doesn't it's a little like someone strangling you slowly.