There is a moment in Mad Men when Joan breaks up with her husband. It is a moment that we, the audience, had been waiting for for seasons and they put a wink there for us, something that Joan couldn't possibly be using in that moment.
See, she wanted a husband and to be the perfect housewife. She did everything right. She followed the rules to be desirable and cute. She dated. She wanted a handsome husband who was a doctor or something like that, something important with a good salary and she found one.
But against her will, she had to keep on working, even after they got married. It pained her, she felt ashamed but never showed it. Against her will too, she had to work next to Peggy and see her evolution and the possibility it entailed. Against all odds, she was valued by her colleagues, by her boss, by her lover. Against all the rules and all the propaganda she had bought and followed willingly, she had to notice and accept that her husband didn't value her the way other people did. Against it all, she missed her job and the self-worth it gave her.
Over the series, we see glimpses of her life with her husband. And once and again he proves to be an asshole, the kind of asshole you don't see coming, and he was a bit of a dangerous one. When they start dating, at some point, in one of the first seasons, he rapes her in the office.
And they make it look like it's all forgotten, except he also puts her in embarrassing situations, doesn't listen to her, makes plans without asking her, etc. It all seems usual, as according to plan (specially when we see what the other men do to any woman they date). And eventually, specially after he starts working with the army and has to leave for months at a time, she notices more and more the difference between being with him and being alone.
And so he comes back, they have a massive argument which she finishes with "and you know what I'm talking about". And that is the moment when we, the audience, know all the things he's done. How it built up to this moment. But it is too many tiny things in Joan's life, maybe she will name them but not now, up until this moment, they exist but they are also the norm, they are also expectable. She may hate him for them, she may even hate herself, but this "you know what I'm talking about" is not any of those moments.
Maybe he cheated on her. Maybe he disappointed her in a very specific way that was the last drop. But they have a story that we, the audience, don't know. Something happened that made Joan realised what was going on and that she could use against him and it wasn't showed to us. Obviously, as I said, that was the last drop, all the other things play a role too, but is the thing that made Joan see clearly.
I think it is interesting as story-telling. It also bothered me a bit when it happened, that very obvious wink to the audience who had been unable to help her in any way. But it was above all so satisfactory. I love what they did with Joan, how they allowed her to thrive.
I hope it helped people who were in bad relationships at the time and who were watching the series that they could be the Joan too.