How to officially let go of a difficult work situation?

I resigned from a high level position at the end of September, so four months ago now. It was a very difficult situation and my resignation sent a strong message to the organization and was also a huge relief to me. I am now able to move forward with my vision and take massive action and I am doing that. My problem is I continue to have difficulty letting go of the anger I have towards the organization and the many people who were a part of why I felt I needed to resign. I have a lot of support from the community and from my family. Whenever I think of and spend time creating my dream job and vision and when I hear about the organization or those still there, I get triggered and get angry. I have worked with a life and well-being coach and have been working very intentionally on self-care, meditation, yoga, etc. It’s all been very helpful and I know it takes practice. It’s just that several times a day, I still get pissed off and it feels like I am giving them power and I don’t want it to intrude on really doing something great moving forward. I guess it’s fear that the organization will try to sabotage or will make fun of my massive action. How do I learn to let go of something that happened but should not have, but did, so I can feel a sense of freedom and move forward with massive action? The anger I feel is draining. Thank you!