"Don't believe anything she says and only half of what she does". Learn it and live it.
Have no expectations from her (like her being around for Xmas for example).
Detach from her. It means don't get angry with her. Don't let her have an effect on your mood.
Think and act, don't feel and react. The "Feel & React" approach is how most drive the nails into the coffin after BD in my opinion. Nothing requires an immediate response so remember that and learn how to validate and respond without injecting your views too much.
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.