I (25M) dumped my ex-narc (33F) 3 months ago on my birthday. I struggle to move on

How do you guys move on? I mistakenly gave her my heart and she abused it. This is the most pathological and selfish person I have ever met. She even had genuine affection for me, which is what burns, because her deeply-engrained distorted lens of morality centers only on herself and her own emotions as truth, never once putting another human being before her own rampant wants. The idea of sacrificing for another is lost on her. She gaslit me. She's so prideful to have done this, as though she has the right to treat me this way and no obligation to repair. She literally said "I have done nothing to deteriorate this relationship" which is asinine. Allergic to accountability, which I only notice because she dodges it in low-stakes circumstances where normal people would immediately take it. My heart is slaughtered, it still whimpers pathetically for her even now after I've seen her channel such great evil, and now she's with another man who she's using like a sucker just like me, who is now taking her on all the vacations and sauna trips I never was able to. I feel like a loser+failure and wish I hadn't loved the wrong person. I'm in a dark place.