I am writing to tell you how sorry I am about what happened last week.
I’ve been meaning to tell «sorry» since then, but I’ve been busy and didn’t have time. I want you to know I didn’t mean to hurt your feelings, and I am sorry that I did. I was really upset after our argument, and I shouldn’t have let myself get so carried away, but sometimes my temper gets the better of me.
Why don’t we get together for a friendly chat so that we can work things out? How about next Friday? I hope you’ll be able to, and I just want to say again how sorry I am.
Lots of love.