One reason I take classes or go to writing conferences or join a writing group is to set artificial deadlines for myself. I know, after years and many books, that although I'm fairly disciplined with my writing, I need external accountability to get a big project done. No matter that I set goals, and often meet them, writing a book is a long commitment that is easily sidetracked.
Like most of you, I can procrastinate like nobody's business when I want to. With me, it shows up as either cleaning or food. I don't usually go in for internet or Netflix comas, but let me loose with a bag of chips, and watch out.