Promise yourself ice cream when you finish?  It always works for my daughter, lol. 

In all seriousness, though, sometimes when I was writing, I'd hit that WALL and... nuthin.  I found only two things that really helped me -- going back and re-reading my earlier work, waiting for my characters to start speaking to me, or just putting it out of mind.  It drove my readers nuts... I'd sometimes go months without updating, and it was sometimes between important chapters (thank goodness they still liked me when I was finished, lol.)  I'm definitely a binge-artist.  I'll just explode with amazing ideas and creativity, and then, ker-flunk.    (I'm there at present.  I actually went into my digital libraries and organized my content today.  That's like doing dishes when you're bored.  Who does that? Lol!)

And, if nothing else... there's always ice cream!