I consider myself a happy ending. It's still a work in progress - at the time of the separation I told my best friend that I thought it would take about five years before I truly came out of it, and that I would need to change my entire life in those five years. So far, it looks like I'm on schedule.
The good things:
I can parent my kid in a way that's consistent with my values, without constant interference and passive hostility. I no longer hear "you're not even trying to be a good mother", or "[Kid] loves me, but she doesn't really care about you". Kid is thriving and we have a warm, fun, respectful relationship (which its ups and downs, like any other). Kid doesn't have a lot of money and toys in her life, but she has friends, books, adventures, participation in her community, the example of a circle of adult friends who embody the values I respect, and a mother who is fully present for her - none of which would have happened if I had not gotten divorced. That is the main reason I consider this whole sorry mess a success in the end.
I live in a home where I no longer walk on eggshells, always waiting for the next landmine to go off. I am no longer the target of someone else's unresolved anger about how life has done him wrong. My mistakes are mine, and my successes are mine too. I come home now and I'm happy to be here.
I'm able to save money. Even though I'm solely responsible for the mortgage, I'm no longer carrying someone else's spending habits. I will be able to provide for Kid's university education and maybe even to retire without having to eat cat food!
My physical health is much better. I no longer suffer from half a dozen vague stress-related complaints (migraines, nausea, joint pain, insomnia ...). I have gained a profound respect for the mind-body connection.
I'm in a loving, mutual respectful relationship with a great man (they do exist!). I now know what it's like for someone to love me despite my imperfections.
I also have made new friends who are creative, smart, principled. This is only possible because I no longer have to worry about what the ex would think of so and so, or whether my friends are acceptable by his standards.
There are downsides - ex isn't one of the out-and-out nutcases that we hear about on this forum, but he's a bitter man with a drinking problem and minimal coping skills, so I still get explosions of anger and insults from time to time. He is quite unpredictable and goes off the rails sometimes Fortunately, it's starting to diminish since he got remarried. He is also difficult about money and owes me a pile.
Single parenting is not a bed of roses. I have 50/50, which is good because it's the best outcome for Kid (and I get time off!) but that also means I have to communicate with the ex more than I would like, and he's pretty rigid. I also have to take on everything from swimming registration to RESPs to the dentist to buying winter clothes. I also have no backup system - no family who could help in a pinch - so if anything goes wrong, I'm hooped. Kid can sleep over with friends every now and then, but I don't want to abuse their friendship, so essentially I'm out here on my own.
Overall, though I have not had a single moment when I doubted my decision to leave. Despite the misery and the struggles, it was absolutely the right thing to do.