Last year I participated in National November Writing Month. I didn't really have a plan going into it but it was pretty fun. I only got around 10,000 words done. Once I hit a few roadbumps I found it hard to get back into it, partially because I wasn't really into my chosen subject matter, and mostly because it's hard to commit to writing 1,666 words each and every day for a month.
This year I'm back at it with, hopefully, a more engaging plot idea and I hope to see it through until the end.