T.S. Eliot's "The Waste Land" is a poem both composed of and intrigued by fragments. The structure of the poem, but also its themes of decay and breakdown within city life, is both representative of the Modernist preoccupation with fragmentation and the dissolution of things. This same fragmentation can be seen as a theme within Mad Men, most notably in the life of its protagonist, Don Draper. As in "The Waste Land," the speaker has "shored" fragments "against [his] ruins," so we see Draper gathering together fragments of his life and his past lives in order to reach the point of total collapse and rebirth we see in the final season.
The earlier answer to this question notes that Mad Men exhibits similar concerns to "The Waste Land" in terms of demobbed soldiers struggling to adjust to the shifted reality of their day-to-day lives, with their coping mechanisms often centering around alcohol. In the character of Draper, there are far more fragments to deal with than simply his PTSD. Don Draper, after all, is not Don Draper at all, but another man entirely, a working class boy who grew up in a brothel and then stepped wholesale into another man's life. In Draper, then, the Modernist themes of isolation, "going through the motions," and living a life one does not recognize can be seen starkly. Draper begins the series living a seemingly normal life with his wife, Betty, but there is always the specter of something else—recalling T.S. Eliot's lines in "The Waste Land," 'Who is the third who walks always beside you?...when I look ahead up the white road/There is always another one walking beside you.' In the Draper marriage, there are three people: Don, his wife, and the other Don, the specter at the back of Draper's mind and his darkest secret. In a very literal way, Draper embodies the Modernist concern, seen in "The Waste Land," that we are not who we or others believe ourselves to be: we are isolated, and at the same time, surrounded by secrets and unknowns.