In long-term relationships ... we are called upon to navigate that delicate balance between separateness and connectedness ... we confront the challenge of sustaining both--without losing either.
It's true that over-apologizing interrupts the flow of conversation and irritates the person who has to stop and offer reassurance, like, "No, it's fine, don't worry about it." But far greater than the challenge of toning down unnecessary "sorrys" is offering an apology when one is due.