It's paraphrased from famous quotes that lament "when I had the energy/enthusiasm/optimism (of adolescence) I didn't have the wisdom/resources (of adulthood) to do anything consequential with it, and once I overcame the poverty of youth (in wisdom/resources) I was too spent/cynical/weary in adulthood".

It suggests a constraint on humans' impact - an inverse correlation between will & power that yields a flattened curve when plotted against time - and implies that we're restrained by nature.

But if that constraint were broken...