Huge difference in Stipp and OP's circumstances.
OP's instinct is to lie, deny and blame - anything other than accept.
How long did it take Nel to get him to admit he'd killed Reeva?
"I made a mistake"............ ????
A mistake? Is there any other word he could have used to minimise the murder even further? I think not.
Yep, at least make it "an unforgivable mistake".