Since I've used that technique, writers block has become a theoretical idea that doesn't ever touch my writing life.
However, I realise that some people don't want to work that way, and so here are my suggestions for beating writer's block!
Engage another part of your brain
headache and feel like your brain is filled with cotton wool, it probably needs a bit of a kickstart. So, get up and walk around the house, make a cup of tea or listen to some music - even better, play some! This will flush out your synapses (that's not a medical term, please don't write in) and your brain will start making connections in new directions that will hopefully get the words flowing again.
Engage your physical bodyThis works on a similar theory to that above - by getting the blood flowing through your body, your brain will also receive a boost of energy that will help it start bubbling in new directions. You could take a walk (this is a solid favourite of countless authors since authoring began), or have a cycle or a run or even do a few push ups if you're feeling really ambitious.
Create a strict schedule and stick to itIf it's more like weeks are passing rather than hours, and you're not getting anywhere, then you probably need to create a strict schedule and stick to it. Personally, I work best with very short deadlines - such as 20 minutes, then water the plants, then another 20 minutes, then do the laundry. Or you may not allow yourself to have your first coffee in the morning until you've written at least 500 words. Which brings me nicely to my final point...
Don't obsess over detailsIf you're getting writers block, it means you're probably working on a first draft. Rewriting is such an important process that most writers will not have a single sentence leftover from their first draft by the time they're ready to publish. So what's the point of getting hung up about a particular adjective or sentence order? It's a waste of time and energy. Save what you've got for getting the first draft down, come hell or high water, not worrying over a word choice or tiny plot detail.
I hope that helps, and if you have any suggestions to add, please feel free to add them as comments below!