I keep blurting out stuff in front of my kid

I was so good at not saying anything negative for a year. Recently a lot has blown up in my face and I have lost it a bit in front of my kid. She witnessed me crying, raging, and saying little negative things about him. And I have stopped now. But I am afraid for the upcoming divorce and him pushing for more custody. This is so hard. How do you do it when you are really activated?! How does custody even work? We already have close to a 60/40 custody split for a 15 month separation. I am so tired