I hate to generalize about this, but it seems to me that for many poets everything begins in early adolescence. (Maybe it's all a puberty rite.)
In early adolescence there are no sharp borders between poetry and other kinds of writing, or between poetry and experience in general, or between a writer and his or her comrades in writing.
Classicism(?)... we (or I) need a new word for this. Since the Romantic era youth has been lock-kneed, stereotyped, as rebellion. But the passion of young poets for literature has as much to do with a secret affinity for the voice of experience. Classicism should not simply be equated with realism or world-weariness (though these aspects cannot be denied, either). Think rather of the notion of hard-won experience. The voice of character & wisdom - of the veterans of spiritual battles, of living itself.
New forms of such classicism appear in every generation - the enthusiasm of young poets for their own literary discoveries, their delvings into the past, the obscure quaint voices of the ancients (or even just the previous generation) - which turn out to be unexpectedly familiar - clear & pungent.
Keats we think of as a Romantic... but he was also classic in this sense. The classiest of the classic.