This still doesn’t really explain what you mean by stating he needs to become ‘a better man’. Have you considered maybe OP is / was in a better position than his ex/partner mentally, emotionally, physically, dare I say even spiritually, than she is / was? In which case abandoning his sense of self-respect and value just for the mindless appeasement of someone here definitely won’t make him a better person. Thhere are too many variables here to jump to conclusions about who was better and who wasn’t.
I’ll use myself as an example here…
I got cheated on when I was 19 only when I decided to start trying to do better for myself by getting in better shape, studying, ditching the marijuana we both loved to smoke and getting more female attention as a consequence because she was worried she would lose me eventually anyway so cheated on me before I had a chance to cheat on her first. I also got cheated on in my early twenties by a girl who also cheated on the next guy with about half a dozen other guys including a sixteen year old school boy - few finers ways to destroy a guys sense of self-esteem huh? Sure I ‘missed’ both, the former because she was my first real girflriend and I found her emotionally comforting and the latter because the sex was great amd she had a killer face and body. But I got over it and realised I was better off without them and dodged a bullet in both cases.
Now tell me at what point striving to your version to be a ‘be a better man’ here when dealing with a woman who is deeply insecure in the case of my first ex, and who was clearly mentally ill in the second would have done me any good when I was in a better place than them anyway?
Now at 28, after spending a few years working on myself, I find myself married to a mentally mature woman who realised she’s not perfect and doesn’t expect everything in my life to have to need to revolve around her or vice versa - rather we accept we are individuals supporting each other to work on something better than the sum of it’s parts. No offence but if I had decided to accept that my ex’s cheating on me was somehow my fault and strived to become better to the obscure and volatile standards of women who didn’t even know what was in their own best interest, then I would have just become a shell of a man by now and be left chasing my own ass.
No offence but I think you’re overlooking the fact that women are all different too and unconditionally telling someone that got cheated on to try to ‘be better’ without considering the specifics of the case and if a guy at any point was ever even ‘worse’ to begin with is just empty “female worship” and that doesn’t do anyone good, neither her nor you.
Most women don't cheat because they're mentally ill.
I understand your perspective, but this is one of the logical fallacies called the anecdotal fallacy. I understand I look like an ass saying this and I'm not trying to take away from your experience.
But, try to step back here into the most general scenario you can.
What's the goal from the man's perspetive?
What's the goal from anyone's perspective for that matter?
To have a happier, more fulfilling and overall better life.
With that in mind, for the vast majority of men in the vast majority of situations it's going to be better for their long term development to just take the approach of self-responsibility.
It's not important what's "right or wrong" or what the truth really is.
If you go out late at night in a bad neighborhood and get robbed, you are at fault. It doesn't matter if it's wrong that someone robbed you. It doesn't matter that someone "should have been better".
I'm reducing the scenario to its absolute simplest with the goal of the person having a better life in the future than they have now, and to do that, just taking responsbility is better.
There's almost no situation where taking responsbility is not empowering. The opposite is to blame the other person. Blame the world. Blame the government. Blame the opposing party. People just blame blame blame and they only weaken themselves.
If you have a very unique situation where you had a mentally ill girlfriend who cheated because of that, then I agree you aren't going to frame it as "I need to work harder in my business, make more money, be more successful and be a stronger/better man."
But.. You should still be framing it as "It was my fault. I need to be a better man" -- Why? Because you picked/attracted a mentally ill woman.
In that case, you should look at improving your own emotional state so that in the future you don't attract that.
Toxic women are attracted and will go for certain types of men. This is just how things work. A female narcissist is not going to be attracted to a strong, self-sufficient man with strong boundaries. Her games won't work. She won't have control. She will move on to a man who is needy and who falls in love in the first week because she is love-bombing him.
It all comes down to self-responsibility no matter what.
It's never a bad thing.
My advice is aimed at improving people's lives, but the real advice that will improve your life will hurt. Most people want the fluffy bandade that gives them some feel-good emotions in the short-term, but will leave them open to repeating the same pain over and over.
Society today is trying to teach you NOT to take responsibility and NOT to see the world how it is. Everything offends everyone and people feel self-justified in feeling offended because "it's not right".
You can either accept society's view and the life that goes with it, or you can take the path of self-empowerment, where you are the master of your own reality and not a single entity on earth has any power over you other than the power that you give to them.
In summary..
Stop trying to explain, understand or make sense of things.
Just take responsibility for as much as you can in your life and push forward with what brings you joy.