They’re disempowering themselves. Describe themselves as a victim of circumstance, powerless and without responsibility. It’s a disempowering narrative. You’re shooting yourself in the foot. In this story that we live, you are casting yourself as an npc.
On the flip side, saying “I can’t” adds authority to your argument. You’re citing an unstoppable force as the root cause of your actions. So it’s a tradeoff that way.
My go to is “Yeah, I’m good. Thanks.”
“The little one has been awake all night, can you please take her so that I can get an hour of sleep?” - “I’m good. Thanks”
See, this would never have happened. (and hasn’t for me) Because I would have used that sentence much, much earlier.
“Do you want to have a baby?”
“I’m good, thanks.”
“I wasn’t asking if you want to eat one.”
“Either way, I’m good, thanks.”