Don’t tolerate it in yourself: ask “why am I feeling the need to undercut myself right now? Because I’m feeling overbearing? Then maybe cool it a bit. Because I want some love? Then show some or open up to someone about what I’m struggling with!”
Don’t tolerate it in others: tell people in a very simple way: “hey, don’t talk about yourself that way” or “Seems like something’s going on: I’m here!”
The world is DYING to put you down, particularly if you are from a vulnerable demographic, whether it’s because of your gender, sexuality, mental health, or WHATEVER.