I think the peak of my 'vitality' - the sheer inner energy of life - was reached shortly after I turned twenty-one; during a particularly beautiful spring; and in a year when there were no formal examinations at medical school - so I could make the most of it.
I suppose this was when I had just 'grown-up' - at least physically. But psychologically there was an effect, too.
Up to twenty-one, it seems in retrospect as if the fact I was still growing lent a certain child's innocence to my aspirations and motivations, which meant I was not fully responsible and therefore my bad choices were more excusable.
I think we all feel this to an extent: there is a waxing livingness about youth that compensates greatly for its moods and tantrums.
But from my twenty-first year onwards, there was an irresistible 'darkening' of my nature; which I now attribute to my living without religion and therefore - ultimately - hedonically, selfishly. I was no longer growing-up; and the special dispensation of youth no longer applied - no matter how much I might wish it did.
In this sense, we can almost live without explicit acceptance of God when a youth, because youth's sheer vitality gives us (unearned, spontaneously) a spiritual communion with nature. We know God/ The gods implicitly - even when we deny such knowledge explicitly.
This natural-goodness ebbs after maturity, and in order not to become progressively corrupted we absolutely must take responsibility to make the right spiritual choices...
But, of course, at just this time of life, a modern person is most immersed in 'career' - as I was; on the assumption that if we get 'career' right, then the other major problems of life will be solved...
I can now see that - in trying to live without God - I was embarking on a futile quest. As I have often mentioned; I had the general attitude of desiring and seeking 'anything but Christianity' as the answer to my existential dissatisfactions. And I also now see that my negative feelings about Christianity were significantly exacerbated by the (apparently) universal conviction that to be a proper Christian one Must be a member of the one-true-church... whatever and whichever that might be.
I should have been a Romantic Christian - and I should have put at least as much effort into thinking hard about Christianity; as I did about politics, science, literature, music and my other enthusiasms. But that would have meant being less existentially selfish and hedonic - which was something I felt I could not cope with. I needed my selfish pleasures and idleness, psychologically to survive - so I reasoned.
The 'peak vitality' to which I refer presumably occurs for different people at different times (according to sex, rate of maturation, and circumstances) - and there sometimes arises a sense of nostalgia for a time when life seemed easier simply because we felt able deal with whatever it might throw at us; so strong was that surging energy from within.
But this optimism of vital-youth is an illusion, albeit a pleasant illusion; and we ought not to project from it onto something special about the time and place when it happens-to-happen; nor to seek to recreate that temporary phase.
Youth is a bit of a 'free pass', because our real business has not yet begun; and by the time we have recognized peak vitality, it is already going (willy nilly, irretrievably); and our true challenge from life then begins in earnest.
If we desire to move beyond futile yearning for lost adolescence, and for our adult life to be a good and positive experience; we must understand it in the context of God - and that means Christianity... of one sort or another.
What sort of Christianity is then our first proper concern.