When I get writer's block I just walk away and do other things in life... Now that can be 15 minutes or it can be a year. I wrote the first 12 pages once and then stopped cold... Didn't even attempt to continue or write something else for a very long time, something like a year. Then, bang, 2 weeks later I had finished the 100+ pages.
Thought sometimes if I go off to another writing project and at least start a few, the ideas come back to me and I am able to return to the previous one.
And as some people have suggested, just taking a day off from writing can do the mind good. Go out and enjoy a park, get a massage, pamper yourself, window shop, walking, swimming, lots of sex

You get the picture, things to get your mind off of what you are working on.
It's like in the movie "Pi", the main character tells a story about how someone was given a task by the king to figure out if a statue was made of gold... The person could not figure it out because the statue was so perfect looking but he could not tell for sure. In frustration his wife told him to take a bath... When he stepped into the bath he noticed that the water rose in the bath tub as he laid down. Water displacement... So, from there he figured out how to tell real gold from fake golf, water displacement. So, sometimes when you are stuck on something, "take a bath"... Literally and/or figuratively...