There are rare few things one can do that are irreparable. Many if not most of us at one time or another have said uncalled for things and been nasty with people. Those true friends of ours will understand this and with a sincere apology, will be willing to forgive. I don't think the idea of "making up for" things is a good way to look at it. what's done is done and we can repair the damage by being apologetic and going forward doing things differently.