For me, inspiration strikes whenever it does, and then leaves just as quickly, and is replaced with motivation and procrastination. When this happens I constantly think about “ending it all” (not my death, but just stop writing altogether). People drive me to write more, and when nobody says anything, I'm just depressed. I'm a sucker for numbers, so when I can see that the numbers are going down, that also makes me feel like a crap writer. There are also better writers around me that make me feel like “what the heck am I even doing here, trying to write a book?”. This has gotten to be more of a rant than anything else, but yeah.