There are days when I absolutely am inspired to write - days where bits of dialogue and interesting plot plots swirl around in my head and torment me until I get them down on paper. I get inspired to write by writing - it's the act itself that causes the ideas to come.
Then there are the other days - the days I have very few ideas and don't feel inspired, and I write on those days, as well. The only way through the uninspired times is to persevere, even if I end up deleting everything I wrote that day. Eventually the spark ignites again, but only if I keep going in the days I want to quit.