I'm not sure that I do. I'll always own up and say sorry if I've done something wrong, no matter how small, but I don't say sorry for every little thing.
In my family it wasn't the done thing. Strength was not giving a damn, and there was no point in apologising to people who weren't listening, or indeed hadn't noticed you'd done anything wrong. And stubborn me always refused to apologise when I was blamed for something I hadn't done. When I was 18 I didn't even say hello or goodbye to people. Things like that I didn't get, the words seemed meaningless to me. 10 years working in retail has cured me of that.
I do, however, apologise to friends for giving them bad news, even when it's my bad news. I did this repeatedly with my friend concerning my dad. I apologised when I told her he was ill, I apologised again when he died. Every time she's told me off, severely. I have to say now I sometimes do it intentionally- her anger at me is easier to deal with than her being upset.
When I had a cold I was getting frequent coughing fits in my therapy session. I would apologise to my T each time, and every time she would say to me 'That's all right,' or something like it. Her acceptance and response really freaked me out. So not used to it.