NotSpaghetti
^To say "I'm sorry, but I don't know what for" is silly, in my view.^ - I agree, diamondlily - and I think that is exactly the language that will make things worse as it sounds like apportioning blame to the other person.
I would want to stress the importance of the other person to me above what has gone before.
As welbeck says:
^i don't know what i have done wrong
sounds like the beginning of a row
rather than an apology.^
If someone thinks they have been wronged, then they should know why they feel that.
If that's justified, then apologised- sincerely. And mean it.
It's not apportioning blame to anyone - it's just asking what has upset them.
If they don't/won't say, then, sorry, I'm not apologising unless I know why and what for.
An insincere apology means nothing.🙄