It took me a long time to realize what has been called "Descartes' Error": https://en.wikipedia.org/w/index.php?title=Descartes%27_Erro...
"'Damasio argues in his well-known book that it is wrong to think that only minds think. The body and our emotions have a key role in the way we think and in rational decision-making'. Since, in his words, 'the body...contributes a content that is part and parcel of the workings of the normal mind', it follows that 'the mind is embodied, in the full sense of the term, not just embrained'. Damasio's theory stresses 'the crucial role of feeling in navigating the endless stream of life's personal decisions....The intuitive signals that guide us in these moments come in the form of limbic-driven surges from the viscera that Damasio calls "somatic markers" - literally, gut feelings'. Listening to your gut reactions, 'the somatic marker...may lead you to reject, immediately, the negative course of action and thus...allows you to choose from among fewer alternatives '."

Essentially, emotion underlies reason. Or, more generally, our choice of goals, reasoning tools, and assumptions can't be chosen purely "logically" -- even as once we have adopted some goal (like logical consistency) logic can help move forward from that. So, rather than "I think therefore I am", it is more "I feel therefore I am".

Or as Einstein put it: http://www.sacred-texts.com/aor/einstein/einsci.htm
"One can have the clearest and most complete knowledge of what is, and yet not be able to deduct from that what should be the goal of our human aspirations. Objective knowledge provides us with powerful instruments for the achievements of certain ends, but the ultimate goal itself and the longing to reach it must come from another source."

As an example, this issue is a problematical aspect of Star Trek's Vulcans. A life can't be lived purely "logically". So, Vulcans would still have to make assumptions and set goals and choose tools of reason emerging out of their current cultural context and upbringing. And those assumptions, goals, tools and culture are to some extent arbitrary in each instance of choice -- even as those choices generation after generation may be subject to evolutionary selection and so are not arbitrary long-term in that sense. But even saying "we do X because it helps us survive" is itself a choice based on a non-logical (yet generally selected-for) gut-level goal of survival. So, Vulcans are misleading themselves and others if they claim their decisions are purely "logical". They may be logical decisions -- but they remain decisions based on the logically-impure values and assumptions which underlie the logical edifice built on top of all that.

Or, as Bertrand Russel says in one of his books (paraphrasing greatly), all philosophers make at least one usually-unacknowledged assumption somewhere, and then they go off building a castle of logic on top of that foundational assumption.

Ultimately, humans are adapted mainly to find happiness in a certain context reflecting our evolutionary heritage.

A rough sketch of that healthy context is mentioned by me here, citing an essay by Philip Hickey, Ph.D called: "Depression Is Not An Illness: It is an Adaptive Mechanism": https://news.ycombinator.com/item?id=15455259

"In order to feel good, the following eight factors must be present in our lives.
* good nutrition
* fresh air
* sunshine (in moderation)
* physical activity
* purposeful activity with regular experiences of success
* good relationships
* adequate and regular sleep
* ability to avoid destructive social entanglements, while remaining receptive to positive encounters"

In general, the further we get away from those basics (and similar) the more likely we are to be unhappy. No amount of philosophical cogitation is going to cover up that unhappiness long-term for most people. Viktor Frankl survived a concentration camp and then created "Logotherapy", suggesting having a meaning in life can help us endure hardships and even find some happiness in pursuing that meaning. So, there is truth in what Friedrich Nietzsche wrote: "He who has a why to live for can bear almost any how." But long-term, a problematical how takes its toll on our health despite the why (including often times leading to depression).

Some people may be more susceptible to their environment than others (as both a pro and a con):
https://www.scientificamerican.com/article/on-the-trail-of-t...
"As Ellis and Boyce explained in their paper, dandelion children seem to have the capacity to survive — even thrive — in whatever circumstances they encounter. They are psychologically resilient. Orchid children, in contrast, are highly sensitive to their environment, especially to the quality of parenting they receive. If neglected, orchid children promptly wither — but if they are nurtured, they not only survive but flourish. In the authors’ poetic language, an orchid child becomes “a flower of unusual delicacy and beauty.”"

And, beyond that, even when you have all those basics, there is the risk of falling into a "pleasure trap", seduced and addicted by "supernormal stimuli" made possible by modern technology:

https://en.wikipedia.org/wiki/Supernormal_Stimuli
"The book argues that human instincts for food, sex, and territorial protection evolved for life on the savannah 10,000 years ago, not for today's densely populated technological world. Our instincts have not had time to adapt to the rapid changes of modern life. The book takes its title from Nikolaas Tinbergen's concept in animal ethology of the supernormal stimulus, the phenomena by which insects, birds, and fish in his experiments could be lured by a dummy object which exaggerated one or more characteristic of the natural stimulus object such as giant brilliant blue plaster eggs which birds preferred to sit on in preference to their own. Barrett extends the concept to humans and outlines how supernormal stimuli are a driving force behind today’s most pressing problems, including modern warfare, obesity and other fitness problems, while also explaining the appeal of television, video games, and pornography as social outlets."

http://www.paulgraham.com/addiction.html
"What hard liquor, cigarettes, heroin, and crack have in common is that they're all more concentrated forms of less addictive predecessors. Most if not all the things we describe as addictive are. And the scary thing is, the process that created them is accelerating."

http://web.archive.org/web/20160418155513/http://www.drfuhrm...
"Once in awhile, a person may actually become aware of important dietary knowledge. Despite the ingenious misinformation campaigns waged by the dairy, cattle, and processed food industries, sometimes a person actually comes to understand the truth about diet. At such times, determined individuals might attempt to change their diet toward whole natural foods—in spite of dire and unfounded warnings from their families, friends, and doctors. But along the way, they are likely to be met with a formidable obstacle — their own taste neuroadaptation to artificially-intense foods. This challenge is depicted as Phases IV and V, wherein a change to less stimulating foods typically will result in a reduced pleasure experience. In the early stages, this process is dramatic because natural foods often are not nearly as stimulating. Scientific evidence suggests that the re-sensitization of taste nerves takes between 30 and 90 days of consistent exposure to less stimulating foods. This means that for several weeks, most people attempting this change will experience a reduction in eating pleasure. This is why modern foods present such a devastating trap — as most of our citizens are, in effect, “addicted” to artificially high levels of food stimulation! The 30-to-90-day process of taste re-calibration requires more motivation—and more self-discipline—than most people are ever willing to muster. Tragically, most people are totally unaware that they are only a few weeks of discipline away from being able to comfortably maintain healthful dietary habits — and to keep away from the products that can result in the destruction of their health. Instead, most people think that if they were to eat more healthfully, they would be condemned to a life of greatly reduced gustatory pleasure — thinking that the process of Phase IV will last forever. In our new book, The Pleasure Trap, we explain this extraordinarily deceptive and problematic situation – and how to master this hidden force that undermines health and happiness."

Now, could humans become adapted in different ways and remain healthy (by some definition of health that supports survival and flourishing as individuals and as one or more species)? Perhaps. But that remains speculation.

All that said, when people are in healthier unstressed situations, most are less likely to end up addicted:
http://brucekalexander.com/articles-speeches/rat-park/148-ad...
"The view of addiction from Rat Park is that today’s flood of addiction is occurring because our hyperindividualistic, hypercompetitive, frantic, crisis-ridden society makes most people feel social and culturally isolated. Chronic isolation causes people to look for relief. They find temporary relief in addiction to drugs or any of a thousand other habits and pursuits because addiction allows them to escape from their feelings, to deaden their senses, and to experience an addictive lifestyle as a substitute for a full life."