See Dr. Susan Heitler quoted in Fitness Magazine.
… People who grew up with critical, demanding parents or bullying siblings frequently apologize as a way to placate others and avoid confrontation. “Early in life, they discovered that expressing regret, whether they agreed with the criticism or not, caused the other person to calm down, and they’ve continued this behavior as they’ve gotten older,” explains Susan Heitler, PhD, a psychologist in Denver and coauthor of The Power of Two Workbook (New Harbinger Publications, 2003). Women who fall into this category often say “I’m sorry” to stop or prevent an argument with their partner. But by habitually jumping in with an apology, they set themselves up to be the one at fault. “If you’re the only one taking responsibility, it reinforces the idea that when things go wrong, you are the bad guy,” says Heitler.
Read the full article here: http://www.fitnessmagazine.com/health/spirit/your-best-you/why-we-apologize-too-much-and-how-to-stop/?page=2