If your apology spends more time on how bad you feel than on how they got hurt, it’s a speech about you.

An apology can quietly become a request for comfort. When most of it describes your guilt, your shame, how badly you have been sleeping, the other person ends up managing your feelings instead of having their own attended to. The sincerity may be genuine and the effect is still a demand. What they need is evidence that you understand what happened to them.

Name the specific thing you did and the specific effect it had, then stop talking. Leave out how terrible you feel unless you are asked. Say what will be different, and keep that part short.