Express the feelings of narrator and your response if something like this said to you.?

I would say,' Its not entirely your fault and no need for sorry'

When someone says as above, u have accept it at the face value. The narrator must have been in distress and apologises. My reaction will be to accept the apology and say" let past be past and do not worry about it".

When someone keeps or says sorry it is all my fault I think it shows a sign of insecurity, unless someone spilled a drink on me!

It is just like surrendering to police by defalter.