Honestly, I've never experienced writer's block. I'd write constantly if I could. What is most difficult for me is having to "shelve" my writing for other responsibilities. It's always there, waiting for me, nagging at me. My characters grow restless. That's when the 2, or 3, or 4 a.m. dash to the computer hits, and I cram in as much as I can before other obligations rear up and another day dawns.