For most of my life I was an atheist; and therefore my life strategy was to be happy in this life.
(Sometimes I self-denied that I was trying to be happy - but all this amounted to was seeking long-term happiness within this life rather than immediate happiness; for example by studying for exams (not enjoyable), or reading dull philosophical discourses - in order to have a better chance of a happier life later.)
Looking back I can perceive that there were periods of my life - particular periods of up to several months together, up to about a year - when I was exceptionally happy: when I was happy in the here and now and looked forward to even greater happiness unfolding, almost inevitably.
For certain periods, therefore, happiness was easy, came easily, lacked the usual conflict between the short- and long-term.
And I can also see (I noticed this years ago, but couldn't explain it) that these periods of extended easy happiness were followed by dark times, miserable times, times when life seemed meaningless and irritating, and when I could not recapture the happiness of just a few months earlier. These times typically lasted severalfold longer than the easy happiness times which preceded them.
A factor which explains this patterns was that the times of easy happiness resulted from successful hedonism; successfully organizing my life around pleasure seeking. And this strategy paid-off - for a while - with greater happiness; but the result of this was to entrench and make habitual, systematic hedonism, as my major life plan and expectation.
Then sometimes luck turned, as it will; but mostly it was a matter of coming-up-against the basic biological principle of habituation: repeating the same stimulus leads to the diminution or disappearance of the response to that stimulus.
(Or more generally, the fact that strict repetition is an impossibility; doing something/ anything for the second, tenth, hundredth, thousandth time cannot ever be the same as doing it the first time; it will always differ significantly.)
The response is typically that of the addict: escalating doses of the stimulus.
The outcome is also like that of an addict: to become addicted to pleasure seeking despite the lack of pleasure; to become wretched and miserable at the repeated self-administering of an ineffective pleasure-stimulus; yet trapped in the pattern because ceasing to self-administer the stimulus causes immediate and even greater suffering.
Thus the once-successful hedonist is trapped in a chronic situation of low-grade alienation, purposelessness, meaninglessness and misery - a state that is selfish and short-termist and exploitatively sinful in attitude and action - trapped in this state by and because they seek pleasure and (for a while) got exactly what they sought!
In other words, the longish dark periods of alienation followed the briefer happy times precisely because they were caused by the happy times; caused by the bad habits that had been ingrained during the happy times.
This, then, is one of the ratchets of sin as it operates in someone leading what is, overall and in world historical terms, a fortunate and comfortable life; the ratchet by which happiness is turned to alienation; and an attitude where the world and everything in it, including the people in it, is seen as a potential source of pleasure and life strategy a matter of using knowledge, reason and experience to extract the maximum of pleasure at the minimum cost of pain (and effort).
It exemplifies how atheism is not just meaningless, in terms of rendering everything that might be of value either infinitely trivial or a delusion, but self-defeating - because it is thwarted by the intrinsic and unavoidable nature of biology as it applies even to the simplest of animals - even an amoeba is subject to habituation.
The state is common, near universal in the modern West, as Thoreau perceived when he diagnosed that the mass of men lead lives of quiet desperation.
Unfortunately, Thoreau's prescription, which I was indeed following and explicitly so, was to recommend a more thorough and individualist hedonism.
What Thoreau failed to perceive - due to his vague impersonal deism/ atheism, as did I, was that Thoreau's remedy was in fact the precise cause of the disease it purported to cure - or rather that quiet desperation was merely a less severe version of the gratification-addiction which would, inevitably, result from following Thoreau's recommended life strategy of paying the minimum in time and effort for the maximum of personal gratification (see the chapter 'Economy' in Walden where this is explicitly stated).
The only escape from gratification addiction in a secular world view is to obliterate awareness - intoxication, a state of perpetual distraction, a state of animal-like unconsciousness - or suicide, with an expectation that death is the end and this will obliterate all consciousness.
Which all amount to the same thing: for the secular hedonist the prescribed cure for being human is to stop being human - either by becoming something else, or by ceasing to be (especially ceasing to be aware).
This is to cure the human condition by killing human-ness - rather like making a 'better world - a world without suffering - by destroying the world.
I take this experience in my life as a reductio ad absurdum of the idea of trying to live for gratification, as an atheist, with a timespan restricted to human life, without a personal God who has personal concern for me.
Any strategy primarily to seek earthly happiness is self-refuting, and leads (deviously, but certainly) to pleasure-addiction and earthly misery; except it be embedded in an infinite frame: which is the quest for eternal happiness
Earthly happiness is then seen as a secondary and contingent by-product of the true primary goal of human life.