When work distracts you from work
One of the most insidious ways in which I can procrastinate on urgent matters is to get side tracked by future important work.
I'm working on project A. Meanwhile, I got a call related to project B--a much longer deadline matter. Call over, I ruminate about Project B, perhaps send ideas to my Project B collaborator, etc. etc. etc. Before I know it, I'm way off track from my goal of working on Project A, which is due very soon.
I do have some success in shifting back if I'm very conscious about it, but if you have any great ideas or experiences with this I'd love to hear them.