Why women leave
Why would someone choose being alone over being with you after many years, after love, marriage, and despite your efforts?
First do not underestimate the effect of fights. You may think they are business as usual but your partner may see them as an escalation. She may have forgiven you for the very same thing before, even many times, but it doesn't mean what you did in the past didn't stay with her like dirt thrown into a well until the well is completely filled up.
Second, as people change, and they do every day, relationship dynamics change. Love is a river and rivers can run dry. At some point, a person who didn't know how to tune you out, may learn to do it. She may block you by moving out of the part of herself that you inhabit, like a snake shedding it's skin or a lizard long it's tail.
You may be further along in the relationship then you were before as nothing stands still, but does that mean you love her the way you did before? If you don't, she may notice and it will change everything. Women do not want to be simply kept, they need to be adored. Women leave because they notice that you stopped loving them. Cheating, lying, not providing for them, disrespect and fighting her on what's most important is how she knows. Love can be like a barren field.
Or it can turn toxic like red tide, killing all living things inside it, when she learns who you really are. You will be surprised how long that may have taken her, especially if you are a manipulative, selfish, overbearing prick.
You may not think you are, and then you will be left saying to yourself that she is wrong for not giving you a chance, if you can even accept that it's over. Or you may know this, and then you will just feel lonely. Will you regret it? Not fully, and that's why she left.
You lost the love of your life? Then you probably deserved it. Love does not leave lightly. You have to kick it and mix it with manure a few times. You have to choke it so it won't survive. You had many close calls, but you prioritized wrong. Speak to your love after death and even in death it will treat you with kindness. Love is not an angry ghost.
Relationships may die.It is not gold that keeps them alive because gold can be replaced and not flowers because they wither, but water because you will always need it. Feel your love, let it come from a place that is most alive in you.