Stephen Spender says

The writing of poetry is an activity which makes certain demands of attention on the poet and which requires that he should have certain qualifications of ear, vision, imagination, memory and so on. He should be able to think in images; he should have as great a mastery of language as a painter has over his palate, even if the range of his language be very limited. All this means that, in ordinary society, a poet has to adapt himself, more or less consciously, to the demands of his vocation, and hence the peculiarities of poets and the condition of inspiration which many people have said is near to madness….

The problem of creative writing is essentially one of concentration, and the supposed eccentricities of poets are usually due to mechanical habits or rituals developed in order to concentrate. Concentration, of course, for the purpose of writing poetry, is different from the kind of concentration required for working out a sum. It is a focusing of the attention in a special way, so that the poet is aware of all the implications and possible developments of his idea, just as one might say that a plant was not concentrating on developing mechanically in one direction, but in many directions, towards the warmth in one direction, but in many directions, towards the warmth and light with its leaves, and towards the water with its roots, all at the same time….

The concentrated effort of writing poetry is a spiritual activity which makes one completely, for the time being, that one has a body. It is a disturbance of the balance of body and mind and for this reason one needs a kind of anchor of sensation with the physical world…. Poets speak of the necessity of writing poetry rather than of a liking for doing it. It is spiritual compulsion, a straining of the mind to attain heights surrounded by abysses and it cannot be entirely happy, for in the most important sense, the only reward worth having id absolutely denied: for, however confident a poet may be, he is never quite sure that all his energy is not misdirected nor that what he is writing is great poetry. At the moment when art attains its highest attainment it reaches beyond its medium of words or paints or music, and the artist finds himself realizing that these instruments are inadequate to the spirit of what he is trying to say.

Different poets concentrate in different ways. In my own mind I make a sharp distinction between two types of concentration: one is immediate and complete, the other is plodding and only completed by stages. Some poets write immediately works which, when they are written, scarcely need revision. Others write their poems by stages, feeling their way from rough draft to rough draft, until finally, after many revisions, they have produced a result which may seem to have very little connection with their early sketches….

A poet may be divinely gifted with a lucid and intense and purposive intellect; he may be clumsy and slow; that does not matter, what matters is integrity of purpose and the ability to maintain the purpose without losing oneself. Myself, I am scarcely capable of immediate concentration in poetry. My mind is not clear, my will is weak, I suffer from an excess of ideas and a weak sense of form. For every poem that I begin to write, I think of at least ten which I do not write down at all. For every poem which I do write down, there are seven or eight which I never complete….

Everything in poetry is work except inspiration, whether this work is achieved at one swift stroke … or whether it is a slow process of evolution from stage to stage…. The work on a line of poetry may take the form of putting a version aside for a few days, weeks or years, and then taking it up again, when it may be found that the line has, in the interval of time, almost rewritten itself.

Inspiration is the beginning of a poem and it is also its final goal. It is the first idea which drops into the poet’s mind and it is the final idea which he at least achieves in words. In between this start and this winning post there is the hard race, the sweat and toil…. One line is given to the poet by god or by nature, the rest he has to discover for himself….

If the art of concentrating in a particular way is the discipline necessary for poetry to reveal itself, memory exercised in a particular way is the natural gift of poetic genius. The poet, above all else, is a person who never forgets certain sense-impressions which he has experienced and which he can re-live again and again as though with all their original freshness….

It is perhaps true to say that memory is the faculty of poetry, because the imagination itself is an exercise of memory. There is nothing we imagine which we do not already know. And our ability to imagine is our ability to remember what we have already once experienced and to apply it to some different situation. Thus the greatest poets are those with memories so great that they extend beyond their strongest experiences to their minutest observations of people and things far outside their own self-centeredness (the weakness of memory is its self-centeredness: hence the narcissistic nature of most poetry)….

There is no doubt that writing poetry, when a poem appears to succeed, results in an intense physical excitement, a sense of release and ecstasy. On the other hand, I dread writing poetry, for, I suppose, the following reasons: a poem is a terrible journey, a painful effort of concentration the imagination; words are an extremely difficult medium to use, and sometimes when one has spent days trying to say a thing clearly one finds that one has only said it dully; above all, the writing of a poem brings one face to face with one’s own personality with all its familiar and clumsy limitations. In every other phase of existence, one can exercise the orthodoxy of a conventional routine: one can be polite to one’s friends, one can get through the day at the office, one can pose, once can draw attention to one’s position in society, one is – in a word – dealing with men. In poetry, one is wrestling with a god.