How do I get over what my boyfriend/ex did?

I was dating sb almost 8 months ago, and i am kind of person who birthdays is a really big deal to me, anyway i met this guy and he knows that about me and he knows that i don't forgive when it comes to my birthday, things were on and off a lot and on my birthday he literally did nothing not even said happy birthday, we were supposed to go out and he cancelled me at last minute as usual , and i told him on that day its my birthday and he said, so what do you want me to do.
I am not a silly person i should have dumped him long time before that since he started to underestimate me and my value and ghosted me but deep inside i always had some hopes and he still cares, he is not interested and my fault i didn't realise that earlier
The issue is he tried to call me back and get back together and i told him no and dupmed him,
I just can let go of my anger and what he did to me i know i left, but its been two months now since my birthday but i still have anger and hate feelings and can't let go or get over it
How do I get over what my boyfriend/ex did?
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