The biggest obstacle to my writing is the errant characters and stories floating around in my head.
Since I was a small child my stories have played themselves out in my head before I write them down. While that helps me immensely because I have a good idea of where I am going before I start to write, it sometimes give me head congestion if I don't start writing right away.
Case in point: I have three novels and one novella in various states of disrepair on my computer right now. All the stories are flitting around in my head at once. Then, two nights ago a fifth started to "talk" to me. It's jus a "snippit" it has no usable plot, just characters walking around the English countryside circa 1920. Perhaps I'm watching too much Downton Abbey or Mr. Selfridge.
A little ibuprofen would be welcome right now.