You may disagree with their politics, television choices or the way they parent their children, but it's not your place to interject your own preferences and particular parenting style. You are a guest, not a voting member of the immediate family. Even if you are the grandmother!
The worst thing you can do is make an excuse. It's a sign that you are not willing to own your actions, which makes for a less impressive employee. When you make an error, own it, apologize, and state a plan of action moving forward.
You've worked hard to build your career, but despite your best professional efforts, a few bad habits may still be chipping away at your success. Don't undermine your professionalism by actions done on auto-pilot that could convey uncertainty or insecurity.
Finish what you start. This seems simple, but doing what you say you are going to do is the first step to establishing a strong professional reputation. If you say you are going to do something, follow through. No excuses.