Mr. Whitman got kicked in the head by a horse, and Mr. Draper got kicked in the head by a "whore." Don's always been ambivalent about this life. Now that he's about to lose it, he wants it all back.
After an entire season of having his sleep interrupted by Betty, the baby, and Conrad Hilton, Don finally had to wake himself up. This seemed to be one of the themes of this episode, as Don put all his effort into to saving Sterling Cooper, and came to terms with the fact that he couldn't do the same for his failed marriage.
When his relationship with Connie was severed after the news that Sterling Cooper and its parent company were being sold, Don was justifiably bitter, saying, "You come and go as you please, and you don't care that my future is tied up in this mess because of you." It's ironic that it completely escapes Don that he just verbalized exactly how Betty feels about their marriage.
Connie replies, "I've got everything I have on my own. It's made me immune to those who complain and cry because they can't. I didn't take you as one of them, Don. Are you?" He's not. And Connie's speech was the horse kick in the head Don needed to stop feeling sorry for himself and start feeling empowered as a man who is actually in control of his own destiny.
Like Connie, Don is immune to those who "complain and cry" at the idea that they don't have something of their own—namely, Betty.
But unlike Connie—who took a shine to Don because he saw a piece of himself in the creative genius—Don, at times, resents in others what he does himself. Seriously though, didn't you reflexively rubberneck and think, "Who you callin' a whore?" It isn't even a pot/kettle situation: Betty hasn't even consummated her relationship with Henry Francis yet. (And yes, she did fuck that guy in that bar that one time, but her extramarital bedpost is still relatively intact compared to Don's, which has been whittled down to a toothpick at this point.)
More ridiculous was Don's insistence that Betty should see a doctor because she hasn't been "herself". The fact of the matter is that she hasn't been herself during the entire marriage—and possibly for her entire life. She's been the woman she was told she should be. The change Don has seen is evidence that she's actually been getting in touch with herself and her wants and her needs, and she's realizing that Don doesn't fulfill them. She was right when she said she deserved more.
But Don was right, too. Betty built herself a life raft in order to jump ship from her marriage. Don wasn't exactly the whole problem—depending on him to make her happy was. And now she's going to depend on Henry. Will she have to go through a second divorce to realize that what she wanted and needed was independence?
Which brings us to Peggy. Earlier, Roger told Don, "You're not good at relationships because you don't value them." Don's relationship with Peggy in this episode mirrored that of his relationship with Betty. He doesn't ask, he just assumes that she'll follow him around "like a nervous poodle," and everyone thinks he does all her work, even him. He's taken her for granted, saying, "There's not one thing that you've done here that I couldn't live without." She lets him know that she's had other offers—just like Betty.
But unlike his interactions with Betty, Don tries hard to win Peggy back. Like many people, Don subconsciously places more importance on the work that Peggy does more than the work of a housewife. It's interesting how in every scene in his office, Peggy always sat on the right, and Don—in the power position—on the left. Now their roles are reversed. And he says everything to Peggy that he should've been saying to his wife, like, "I've been hard on you, but only because I think I see you as an extension of myself. And you're not."
Perhaps Don took Roger's comment about valuing relationships to heart, because he stresses to Peggy, Pete, Lane, and Roger how indispensable they each are. He seems to know exactly what to say to everyone to make them feel valuable—except for his own estranged wife.
Or his children, for that matter. Although he does try.
Still, his efforts are paying off in some ways. Peggy needed that validation from Don, and now she's sure of her worth—and it doesn't involve fetching coffee for Roger.
Joan—and Roger—however, always knew exactly how valuable she was, and is.
Trudy's pretty valuable, too. She's becoming a Lady MacBeth of sorts, and is proving to be instrumental to Pete's success. It's yet to be seen if he knows this.
Unfortunately, though, the eldest Draper kids are merely afterthoughts. Are they really gonna live with Carla for those whole six weeks that Betty is in Reno?
At the end of the episode, the closing song included the lyrics, "The future is much better than the past. In the future, you will find a love that lasts." Betty's face seems to imply otherwise. Like Don said, "Something happened—something terrible—and the way that people saw themselves is gone." We shall wait and see.