How often do you say "I'm sorry" when what you actually mean is "thank you"? I know I'm guilty of this one - in fact, I feel guilty over just about anything. Because of that, I'm quick to apologize for something that results in someone doing something for me.
For example: as a vegetarian, sometimes people will make special veggie options for meals. I'll apologize for not eating meat, but I'm not sorry I don't eat meat (sorry, not sorry!).
Rather my 'guilt' resides in someone going out of their way to accommodate. I'm not sorry; I'm appreciative of someone's actions.