If you're just not up to completing a task, for example, writing a character's backstory, get it started. Write the file name and date on the card. Next time you draw it, open that file and work on it some more.
This is such a forgiving system. I've gone months when I forgot all about opening the box. In fact, that's what prompted this post: I just started using it again yesterday. It's reassuring to know it's still there, patiently waiting, and just as useful now as it was months ago....