I just wait it out, inspiration will hit me again eventually. I find it better not to force the issue, let it happen naturally for my best work.
http://www.creativity-portal.com/prompts/imagination.prompt.reload.html here is a site i use for writing prompts...I also have a ton of sites listed in the writers forum on here
For some reason I can't write when I'm in a good place in my life, or happy. For me, my best writing comes out of the moods I go through and I'm able to be more descriptive when I can relate and feel what I'm writing. I suppose it's because writing is a form a therapy. I'm also horrible about procrastination. I'll have the desire and interest in writing, but get distracted easily. So many books have suggested pulling away from those distractions and really I have no one but myself to blame for how long it's taken me to write my book, but I think I still suffer from ADD.