most addicts feel awful in the after math.....remember the body has now assimilated the drug use and DEPENDS upon it.....when the drug is WITHDRAWN the body goes ape sh!t. which is precisely why addicts will return to the drug, to feel "better" or "normal".
withdrawal symptoms vary from person to person and from drug to drug. rest, healthy food, and a positive outlook can go a long way. however, that is all up TO HIM.
good for you in maintaining your schedule and your self care.