It doesn't sound like it was all your fault, nor was it all theirs. It sounds like two people who care very much for each other realized that the patterns they were reinforcing were not good for either of them, and took painful steps to keep the relationship they could. I'm really sorry you're in this position now, but I'm also really hopeful that you see the good in your decision and that you were able to make it calmly despite the emotions of the situation. That's a crappy consolation prize but maybe you'll learn and grow your emotional toolkit to make the ability to handle situations like that even stronger.
Something that helped me to become better at communicating my feelings (and communicating when I couldn't manage it well) was reading about mediating other people's conflicts. Self help / self regulation books and the like weren't helping me to navigate these situations but ones about mediation in the workplace or at home helped me to see the types of patterns that played out in my relationships. Discussing these techniques - like lots of "I feel" statements and no "you make me" statements - with my partner and agreeing to try them gave us the emotional space to really start practicing better management of ourselves.
I hope I'm not overstepping with this, but I am scared alongside you about starting anything else this quickly afterwards, and especially this intensely. It doesn't sound like you're being kind enough to yourself to give enough time to process, or to build up the emotional management skills you're hoping to. Coming on so strongly to someone who's just been through something like this doesn't speak very highly of this guy's character either, from where I'm sitting (just north of total ignorance, but still).
Whatever happens, I hope you find the space and peace to train those relationship and emotional skills you want for yourself, and the person or persons who help you to reinforce them.