Sleeping

From the helpfile:

Usage: sleep

Sleeping greatly increases your regeneration rates. The only drawback is
that you are unconscious and easy prey to anyone who might be passing by.
Make sure you only sleep in a safe room.  When first starting on Nodeka, 
resting and sleeping will make little difference, as you will most likely 
regenerate 20 points in each category.  This is done to simply assist you when
you first begin your journeys here.  As you grow more and more in power, 
resting and sleeping will have a much greater affect.

In addition, while you are sleeping you cannot be pulled by those who you are
following. Often times this is needed.

For more information, see: help wake, help rest, help stand