Contact with Ex

I am still sad my ex decided to leave and start a new family. How do I process this and heal properly? It has been 5 years.

How do I let go of all hate and anger and feel neutral. I feel best when I have no contact, but we share children together so this is not possible. Every time I get a text from him I feel anxious or annoyed. I would like to feel neutral.

I also blame my trust issues on this failed relationship so I am scared to put myself in vulnerable dating situations.