It's cheap to say "I'm sorry." It's supposed to absolve a person of blame, but it doesn't cost anything.
Changing behavior is a bigger investment, because it takes real energy.
In this sense, if you ever really mean "I'm sorry," it might be a good practice is to disallow yourself use of the phrase. I have a friend in a big law firm where it's actually office policy that they're not allowed to apologize to clients, because they're supposed to speak by way of results, instead.
Changing What You Say is a Good Way to Change Your Behaviors
If you disallow yourself the use of "I'm sorry," you cut off the easy escape route. Saying "I'm sorry" does allow you to make a minimal-shame escape from whatever it is you've done. If you force yourself to disown the phrase, then you have to sit there with the guilt of some behavior, without a cover-up. And negative experience, psychology has shown, is the strongest incentive to changing bad habits.
Complaints are Just as Cheap
Like "I'm sorry," habitual complaints are cheap, too. Like apologies, they are a no-cost escape from negative feeling.
For example, D.H. Lawrence was a misogynist, bullying novelist who tended to complain a lot about things, without changing his behavior in the world. A bullish, bloated complaint could make him feel strong without obliging him to change behaviors. In a typical letter to a friend in 1922, he complained about where was living, in Australia. "Australia," he wrote, is "so empty.... Everything except meat is exorbitantly expensive.... It is all very irritating.... You never knew anything so nothing, nichts, nullus, niente, as the life here.... It all seems to empty, so nothing, it almost makes you sick." That's a tone of voice he often uses in his letters: He pretends to flex a muscle when he's actually wallowing.
A complaint can be a way to force other people to carry some of your negative feeling. You flex a muscle in the form of argument, without making changes, and so unload your frustration onto others. That's called "projective identification"--the diffusion of your emotion onto others. When a habitual complainer like Lawrence doesn't want to sit with a feeling, himself, he can increase negativity among his friends, and so make others feel his negativity for him. Other people's empathetic frustration lightens the frustration he'd otherwise carry in isolation. A complaint unloads a burden by passing it off.
In addition to this, a complaint is also an externalization: It finds blame in things that are external to one's self.
In this light--as in the case of "I'm sorry"--it can make sense to disallow yourself any complaint you make too often. A complaint can function, after all, like a ritual, in which you regularly, and without personal cost, release some negative feeling. And if you were not allowed to complain--if you had to sit with the fact that you were the biggest grump in an otherwise sweet Australian town, for instance--you'd likely put more energy into changing your behavior.
Making a vow to stay away from certain words can stimulate personal change. You force yourself to sit with the reality of negative feelings. And facing reality is a basic step to changing it.