I learned about the supposed cycle of civilisation, and its despair inducing futility, as a pre-adolescent child. You know the one about civilisations having a barbaric youth of growth, an adult maturity of... civilisation, and then... inevitably... a senescent, decadent decline.
There are many variations; but here-and-now, for us moderns, this is essentially a fake insight.
Why? Because we are living in modernity 200-and-some years after the industrial revolution, which was the greatest non-cyclical change in the history of Men (the first and greatest non-cyclical change was the invention and spread of agriculture).
Insofar as there is truth is the cycle of civilisations idea, it refers to the agrarian era - that part of human history between the agricultural and industrial revolutions. Indeed, if there is any meaning to 'civilisation', it is restricted to the polities, empires, nations of that era.
But the idea has deep errors built-into it. One is to reify the abstraction of 'civilisation' - as if it was 'a thing', and a primary thing at that... rather than merely a by-product and a collection of creative causes.
By their revealed preferences - by what they actually do, nobody at all ever puts civilisation first; nobody builds, enjoys, defends or indeed genuinely cares-about a 'civilisation'.
The so called civilisations were not made by people who were trying to make civilisations - which is why, after a while, they 'decline'. They decline mostly because nobody is even trying to sustain them (whatever they are) - people always have other priorities - and these priorities differ by time and place.
Looking at a couple of the longest-lasting 'civilisations' - the Ancient Egyptians (3000 years) and the Byzantines (1000 years) were religious societies, who strove to sustain and defend and live-by their religion, primarily. Everything else was secondary, and dispensable - as revealed by the end of the Byzantine empire with the fall of Constantinople in 1453. They were defending their religion - to the death; and they would not sacrifice their particular Christianity to the imperative to save the city or the civilisation or empire*.
What's my point - what am I trying to say? That we should not be sucked-into an insincere and futile attempt to save something that doesn't really exist and nobody genuinely cares about as a number one priority. But instead should try to save and promote that which we most deeply value.
At best, a civilisation is a temporary and grossly flawed thing of mortal and material life. We, personally - as immortals, will outlast all present and possible civilisations.
At most a civilisation is merely a means to an end - and that end should be spiritual and eternal.
*Note: The impulse of romanticism in Germany led to a distinction between civilisation and 'Kultur' - in which civililisation was seen as superficial, explicit, artificial and French; while Kultur was seen as deeper, more a thing of the heart and soul, and German. By this distinction, civilisation might be subject to cycles and to be a thing that could collapse and disappear; but Kultur would be something that might prove indestructible - remaining viable and powerfully motivating hidden, coded, latent, inexplicit, and beloved.