Why do I frequently become defensive?


I have noticed that I frequently become defensive and am curious about why this is such a default reaction for me. Recent example:

C: Nanny said several weeks ago that she needed to talk to us about her payroll. We offered to talk any day last week after work but she said she was busy. Today she says “We need to talk about payroll, please.”
T: She is mad and blaming me, even though we offered to talk any day last week
F: Defensiveness
A: Defend myself by saying “We’ve been ready to talk for a while. We offered to talk any last week but you said you were busy.” I don’t say this out loud but in my head (and perhaps it comes through in my tone) I am thinking, “this is your fault, not mine.”
R: Create tension and disconnection

I know the defensiveness is coming from my thoughts, but it also feels like there’s something deeper like an inner self doubt that causes me to want to intensely and urgently defend myself. Of course I can change the thought but maybe there’s something deeper I need to address.

Intentional model:
C: Nanny said several weeks ago that she needed to talk to us about her payroll. We offered to talk any day last week after work but she said she was busy. Today she says in an annoyed tone “We need to talk about payroll, please.”  I realize the “annoyed tone” is not neutral but I can’t think of a neutral way to say it.
T: She still wants to talk about this
F: Neutral or compassion/understanding
A: Simply say, “Sure, when would you like to talk about it?”  Don’t defend myself or blame her or me
R: Reduce tension in the room. Address her need to talk