Be specific enough that an apology has something real to repair.

A general apology leaves the injury exactly where it was. Sorry for everything, or sorry you feel that way, covers ground without touching anything, and the person listening is left holding a hurt that has still not been named by the one who caused it. Naming the particular thing is what makes an apology land.

Say what you did, not how you feel about yourself for having done it. I interrupted you in front of your colleagues and it was unfair is a repair, while I am a terrible friend is a request for reassurance. Then say what you will do differently, and stop talking.