My (26F) ex-boyfriend (29M) emailed me asking to get back together. How do I stop feeling so angry?

Long story short, it was a tumultuous year and a half relationship. We had our good moments and our bad but I eventually figured out that the relationship was toxic. He had a general anxiety disorder that manifested in such ways that made it very difficult to be with him, even though I loved him so much and gave it my everything. Breaking up was extremely hard because I had such empathy for his mental illness and understood a lot of our very bad moments resulted from it. However, it took a huge toll on my happiness and my own mental health and I had to end it.
Yesterday, three months after the breakup, he contacts me despite my wishes for space and time, with a very long and well-composed email detailing all the ways he?s changed his life. He got off the SSRI (anti-anxiety drug) that he attributes a lot of his complacency and detachment to, he started working out again, he started eating better, he spoke to a bunch of his managers to get his career back on track. He asked me to give him another chance.
All this is great for him, but I feel so angry. I feel such painful rage boiling inside of me and I just. I think I can rationally reason out part of why?he hurt me, he has the audacity to email me despite me asking for space, not once in his email did he show he really understands what I?m going through right now
I?m not going to get back together with him. I doubt that, despite struggling with his disorder and issues for seven years, a breakup and three months suddenly has him fixing it all. If this is true, then he really didn?t try hard at all in our relationship. I just want to stop thinking about it. I want to stop feeling so angry and resentful. It?s really not me. But how?
TL;DR: My ex-boyfriend wants to get back together with me. I very decidedly do not want to give him another chance but I feel so angry every time I think about it. How do I stop feeling this way?
**Edit w. update**: I emailed him back telling him much of what I've said in the post above. Then, he sent another email asking me to clarify additional things because he really wants leave me with the "right" perception of him. I wanted to be as empathetic and help him as much as I could, so I messaged him clarifying a few of the things he asked (what the biggest issue was, if he wasn't anxious would I be with him), he also asked me if I believe I did anything wrong. I started feeling even more angry and there was some back and forth, me asking for space multiple times and him still asking questions. Finally, we've stopped and I think I've made it clear that I really do need my space. I know. I need to be more firm.
This has honestly just drained me. I'm so burnt out. I have nothing more left to give him. Here's a big ol sigh.


Source.