I am so not feeling writing today. This happens from time to time during NaNoWriMo and sometimes I take a break, but other times I set my timer and I go to work. Through NaNoWriMo I learned that I am very capable of sitting down and pushing through a block and coming out the other side with good work. No, I am not saying that those words are the best or even something that I will keep in the end but they help to move me forward. Sometimes moving forward is all I need to develop my characters, my plot, my novel. So in November I plan to write for two hours per day. I set a schedule for myself and I sit the chair and I let the words come. If nothing comes, try again the next day and keep going until I reach 50,000 words.
Breathe, plan, do 
Wow. Familiar. Great description here! Last year it overwhelmed me and I didn’t write.
I have this trouble with writing as well sometimes. It’s not always a writer’s block per say, more of a lack of motivation to even weave a story. And really, sometimes, it’s just not being in the mood. Depending on the type of story you’re writing, sometimes it can be difficult to get in the right mood to be on the same level with the mood of the story. The hardest part, I find, is getting started in times like this. So you just push hard, and know you can take a break after while and come back. Usually that helps. And of course making sure you have music that can help set the mood helps as well.