Because they are very hyperactive, they tend to become nervous and start biting their nails which is an obvious sign of nervousness. As mentioned earlier they express their state of mind through their body language, hence we can make out when they are anxious or nervous. They need to engage themselves in activities that keep their finger busy like knitting. Playing a keyboard etc. manicures can also be of help at time to overcome their habits. Sometime they are unorganized. And do not sort out things and then get stressed up later when things start becoming messy around them