It's amazing what personal hells a person will willingly put themselves
through when they feel guilty.  Some people, when they feel guilty, can get
physically sick.  Others can get headaches.  Some just sit around and
agonize over what they did and how they can reverse or remedy it.  Very 
often, a good person can say something hurtful when they're frustrated and
emotionally stressed.  It's never a good thing, and it's definately not 
excusable, but it can happen.  And sometimes it happens to someone they love
very, very much.  That's when the guilt really gets overwhelming.  Sometimes
it keeps them from sleeping, and sometimes they feel so sick that they think
they'll throw up.  Sometimes, though, they just curl up into little balls
and cry, because they feel so much guilt.  A lot of times, when something
like this happens, it takes a while to make it better.  Other times, if the
person is very, very lucky, their loved one will understand a little, and
accept their apology.  It is very confusing, how emotions affect people.  It
makes us lash out at people we love and trust, just because there are other
people whom we want to lash out at, but we're afraid of what will happen.  
And then, we feel incredibly guilty about hurting someone so close to us.  It
really is the worst emotion in the world, guilt.