1. commit to a chapter per day. it'll go faster than you think. then, rather than open your document, stare at it and feel the pressure of 50,000 unwritten words, you'll just have to write a chapter's worth. maybe only 200 words. or 500. maybe your character will put 1,000 words in that chapter. it doesn't matter. that chapter will be done. and in five days, you'll have five chapters done. five more than you would have if you had let the pressure of the unwritten novel freak you out.
2. write really short chapters.
go. write. be merry.
turn your fingers into writer's block