Relax. Nervous habits like nail biting and hair pulling are usually just ways for your child to calm himself when he's facing challenges or feeling nervous. Rarely are they a cause for concern (talk to your pediatrician if your child is pulling out large clumps of hair or causing physical harm to himself), and most kids outgrow them by age 6.
In the meantime, here are some other ways to help him cope -- and even break his bad habits:
* Find a substitute. Figure out what seems to bring on the behavior. Whenever you see your child doing it, let him know that you've noticed he seems anxious, and show him different ways he can make himself feel better, such as taking deep breaths, rubbing a stuffed animal, and playing a pretend piano on his lap.
* Establish routines. Make transitional times, like going to preschool, as smooth, predictable, and fun as possible. Encourage your child to say "good morning" to the sky when he wakes, let him get dressed and eat in the same order each day, and have him wave bye-bye to the house before he leaves. This will give him consistent cues to what's about to happen and help make him less anxious.
* Give him a guardian. Offer him a picture of the two of you or a tiny stuffed animal, to help him feel safe when you're not around.
* Offer cuddles. Snuggle together, or simply put a hand on his shoulder when he seems nervous. A little TLC can go a long way.
* Grant rewards. Give him stickers for the times he goes habit-free. When he collects, say, four, let him trade them in for a treat.