Should I Just take the Half-Day?

I canceled a half-day assignment, only to accidentally pick up another half-day for tomorrow. I really want a full-day assignment (and the full pay), but I’m hesitant to cancel again just to try my luck. I’m pretty sure I could grab another assignment, but you never know.

How do you all feel about half-days? This one would have me going in for just an hour, which feels like a good deal. Would you keep it or risk holding out for something better?