It is fascinating to read how different thinkers may approach the same question. For instance, Epicurus the Greek philosopher said one thing about human existence, giving it one evaluation, whereas Maximus the Confessor described it in far different terms from his own Christian perspective.
Epicurus thought that Everything we do is for the sake of freedom from pain and anxiety (Letter to Monoeceus). When Epicurus speaks of "pleasure" as being the goal of a happy life, by that term he means freedom from pain and suffering, relief from our ostensibly natural state of being which is painful and needy. For Epicurus, this is just the way things are. The world is such that humans naturally seek pleasure and try to avoid pain, and the wise man is one who (in accordance with Epicurus' teachings, of course) knows how to do this effectively.
Maximus the Confessor is not ignorant of this reality, but he thinks this is an unnatural state of affairs for humanity, one brought about by mankind's evil. Maximus defines evil in a couple of different ways, but one suggestive definition is this: Evil is the thoughtless motion of a thing's natural powers towards some other end than the one natural to them, as a consequence of a mistaken judgment (Quaestiones ad Thallasium, 11; translation mine from Romanian). For Maximus, then, evil is not primarily suffering or pain, but is defined morally: it is a straying away from the natural order of things because of a mistake in judgment. Maximus here adopts a kind of ethical intellectualism that was particularly important for Origenians throughout the early ages of the church.
For Maximus, then, the situation of mankind's pursuit of pleasure and flight from pain came about because of humanity's mistaken judgment in obeying the disastrous "advice" of the serpent in the garden (Quaest., 12). Through this mistaken judgment, he became convinced that the true good, the true fulfillment of his nature, would come about through the pursuit of pleasure by means of the five senses. The continuous pursuit of bodily pleasure, of course, was found to be intimately connected to the experience of pain: And because any evil disappears along with the modes that produce it, mankind, learning through experience itself that every pleasure is certainly followed by pain, was thoroughly determined to seek pleasure and to flee pain. For the first he would fight with all his strength, the second he would combat with all his striving, imagining the impossible, namely that through this awareness he would be able to separate the one from the other (Quaest., 13).
There is one thing I want to emphasize here: what for Epicurus is natural and inevitable, for Maximus is eminently unnatural and unintended. Epicurus speaks from the perspective of Greek philosophy, which sought to explain the world as it was, and in the case of Epicurus, without aid of divine revelation. Maximus, on the other hand, cannot but evaluate things from the perspective of Christian revelation.
The lesson we learn is that Christians and non-Christians do not approach the world starting from the same premises. What is obvious to one group is nonsense to the other; what is natural and good to one group is anything but to the other. If this is so, then it is hardly a surprise that non-Christians might find some Christian perspectives on things to be utterly nonsensical! And the same is certainly true vice-versa. This is why dialog between believers and non-believers can be so fruitless at times: they don't agree on the first things (basic principles, axioms, standards of judgment, etc.), and so they inevitably find they disagree vastly on later things as well.
What is needed is a willingness to listen to the other side and try to see things from different eyes. This is a quality notably absent in the case of many theologians and philosophers, by the way, who will in published writing confess their ignorance as to the meaning of another's statements, the plausibility of another's arguments, etc. There may be a time and place for that, I don't want to say that nobody could possibly propagate an unintelligible or implausible position, but certainly an effort must be made for understanding first. Both Maximus and Epicurus note the human tendency towards pleasure and away from pain, but both ascribe to it very different meanings; both evaluate it very differently.