An apology with a “but” is a press release, not repentance.

An apology that turns a corner into explanation stops being an apology. The word after it does the real work, and the real work is defending yourself. What the other person hears is that you have reviewed the incident and found yourself mostly innocent. Repair asks for something harder: naming what you did and leaving the sentence there.

Next time you owe someone, say the shortest true version and then stop talking. Your reasons can come later, if they ask for them. Notice how badly you want to add context, and let that wanting be the sign that the apology has not landed yet.