It was always going to take a miracle to get Don and Megan's relationship to work out; they both had different preoccupations and came from different eras. Don was a man of the 50s; Megan was emphatically a woman of the 60s, and the two don't really blend well together, as their relationship proved. But also it was their ambitions that pulled them apart. Megan wanted an acting career, and to do that she had no option but to head West. Don liked California but to move there would have been to retire at 40, since it proved to be an elephants graveyard for advertising. While Megan was clearly a good person, and she certainly had the look of an actress, it was never really indicated she was cut out for the job. Her breakout role was on a trashy soap-opera and she never really got much further once she left Don. In fact, it was often implied she'd got most of her roles due to the influence of her husband. Her meeting near the end of Season 7 with Harry Crane (however despicable his actions were) also suggested she didn't have the nous to get along in such a cutthroat industry.
