The first couple of nights I found I wasn't as tired.  The energy level increases as you rid your body of all the toxins and junk you were use to eating.  Maybe you could try reading a book or listen to some soothing meditating music. (Like you would hear when getting a massage).  Also, make sure that you aren't doing any heavy activity a couple hours before you go to bed.  I find it harder to sleep if I do this.  I hope this helps.