The Italian word 'stanza' means 'a room', and a room is a good way to conceive of a stanza. A room, generally speaking, is sufficient for its own purposes, but it does not constitute a house. A stanza has the same sense of containment, without being complete or independent.
At four lines, with the quatrain, we reach the basic stanza form familiar from a whole range of English poetic practice. This is the length of the ballad stanza, the verse of a hymn, and innumerable other kinds of verse.
At somewhere around 10 syllables, the English poetic line is at its most relaxed and manageable.
The iambic line, with its characteristic forward movement from short to long, or light to heavy, or unstressed to stressed, is the quintessential measure of English verse.
The iambic pentameter owes its pre-eminence in English poetry to its genius for variation. Good blank verse does not sound like a series of identically measured lines. It sounds like a series of subtle variations on the same theme.
The voice is raised, and that is where poetry begins. And even today, in the prolonged aftermath of modernism, in places where 'open form' or free verse is the orthodoxy, you will find a memory of that raising of the voice in the term 'heightened speech.'
For poets today or in any age, the choice is not between freedom on the one hand and abstruse French forms on the other. The choice is between the nullity and vanity of our first efforts, and the developing of a sense of idiom, form, structure, metre, rhythm, line - all the fundamental characteristics of this verbal art.
In the writing of poetry we never know anything for sure. We will never know if we have 'trained' or 'practised' enough. We will never be able to say that we have reached grade eight, or that we have left the grades behind and are now embarked on an advanced training.
There is no objection to the proposal: in order to learn to be a poet, I shall try to write a sonnet. But the thing you must try to write, when you do so, is a real sonnet, and not a practice sonnet.
A really interesting and happy time was when I first went to Florence as a student and studied Italian. I was living in a pensione on an allowance of £40 a month, which was princely. I did a lot of work and enjoyed myself immensely.