does a gardener only water their flowers after they've bloomed? does a farmer only tend to their crops once they've shown fruit?
so why do you believe you should only write once you've got something to say? why do you only draw once you've got an idea?
if you really want to grow your craft, tend to it faithfully, and not just when you've got the inspiration or motivation to do so.
just as a flower only grows after it's been watered, the words you want to say will arrive after you start writing, the idea will arrive after you start drawing—inspiration will arrive after you start working.