Do you ever wish you could apologize?

Are there ever times when you wish you could apologize but you missed your chance?

I have a difficult time apologizing. I'm much better at it now than I used to be, but you can't go back and change things.

So here it goes:

I'm sorry, boy and girl who were talking on there cell phones in the lab that I was teaching in. I'm sorry I yelled at you. To my credit, I didn't know that you just found out that your mom had cancer or that you were talking to your husband in Iraq. All I knew was that you were talking on your cell phones loudly while I was trying to teach. I should have spoken nicer or been more tactful; instead I got angry and that was wrong.

I'm sorry, but you'll never know that because I don't know who you even are. I hate that.