What motivates me to write is when i'm excited about what's going on with the boys (as far as fanfic is concerned) Like this past visit to London and having them all live together in one house, hello? I felt like if I didn't write about the experience my brain was going to burst. It has to be something like that to get me to write. I love writing in general but I find it's always hardest for me to just start.
On the other end, when nothing is happening in the fandom or something I really am not happy about (like the NKOTBSB) I find no motivation at all to write a thing. (like now, they are no longer in London so sudden'y i'm not at all interested in writing anymore lol) Also, like so many of you have said, real life issues getting in the way. During the school year, I have 0 inspiration to write a thing or if i'm really really stressed out, it's not going to work either because I always feel this guilt like I should be working on a solution to my problem instead of writing fanfiction. LOL