If your wrist hurts, you should definitely take a break too!
And yes, wrist pains and numb fingers are due to drawing - or rather, due to keeping your wrist/hand in the same position for a very long time. When you put a lot of strain on your hand for a very long time without taking breaks properly, the sinews in your wrist can become inflamed and/or damaged. The sinews in question are the ones running from your elbow down into your hand, and they connect via the outside of your hand (the side your little finger is on, not the side your thumb is on), so usually, people who have pushed themselves too hard feel their little finger going numb as a warning sign.
Not everyone gets numb fingers, though - some just get wrist pains. Basically, if your drawing hand is hurting - TAKE A BREAK. Stretch your wrist, and try to relax. Carpal Tunnel Syndrome is a big deal, and should be taken seriously. If you're not careful, you might require surgery to recover from it - if you can recover at all. Some people get permanent injuries.