Let's imagine someone who possess extremely negative personality traits. For example, let's imagine someone who is an incorrigible drug addict. Each day, he bounces from bender to bender. He is indiscriminate in his drug consumption. Like many addicts, he steals in order to consume more drugs, and he sells himself. He spends every waking moment of the day - and a large majority of sleeping moments - under the influence of highly destructive addictive substances, compromising his health, his relationships, and his ability to meet the basic needs of social interaction. He is in a constant state of denial about his addiction, and he lies compulsively.
Now let's consider the polar opposite of this extreme. Let's consider someone refuses to ingest any substance that isn't fully vetted by medical science, conclusively proven to provide health benefits. He will even ingest foods he finds completely disgusting, simply because they are medically proven to provide health benefits. He spares no expense on pursuing healthy ingestible substances, spending the vast majority of his earned income, and even incurring manageable debt loads in some cases, to procure healthy foods, supplements, and medicine. He invests a great deal of his time studying medical research so that he can determine exactly what is beneficial and what is not. He also rigorously adheres to every law on the books, no exceptions. He tells the truth, not just all the time, but he goes out of his way to speak the truth, even when doing so makes other people feel awkward.
Shall we agree that these two men, with respect to their actions, are polar opposites?
Now, a number of people will a "resolution" here in noting that "the truth lies somewhere in the middle," or that both of these men are examples of "extreme" behavior, which can be corrected with "moderation."
But consider the alternate possibility. Consider the possibility that a third man ingests massive amounts of recreational drugs, but also massive amounts of substances with proven scientific health benefits. When he interacts with others, 50% of the time he lies egregiously and the remaining 50% of the time he speaks truths that make people feel awkward. All of his time is spent consuming either recreational drugs or health foods and supplements. He spends all of his money on one or the other kind of substance.
Note that this third kind of person is also a sort of "equilibrium" between the "extreme" addict and the "extreme" health nut.
Sometimes a "happy medium" consists of a careful avoidance of unquestionably negative behavior. But in many cases, it consists of people who readily engage in various kinds of destructive behaviors that can be rationalized to "balance each other out."
Hence the dieter who eats M&Ms and then punishes herself with exercise (recipe for bulemia). Hence the many people in the world who spent their youth in a drug-induced stupor and their later adulthood pursuing healthy living. Hence the work hard/play hard crowd. The list goes on and on.
Sometimes it's important to remember that being somewhere in the middle is not an inherently good thing. What's important is not how extreme or moderate one's life is, but how correct it is. You can't cheat the truth.