I had thought this was about apologizing in general. :0 Oh well, might as well just make it about that topic.
Apologizing is really mandatory in any kind of relation. But communication is the most important, and by communication I mean really expressing your thoughts and making them clear to your opponent, not expressing your thoughts and making them clear to the wall behind your opponent. Lack of communication is the #1 reason for failed marriages and pretty high on the scale of "reasons for war".
Yeah, look at me, I made this pointless thread into an important life-lesson. Now continue worshipping me.