Inspiration is always a very uncertain thing; it comes when it chooses, stops suddenly before it has finished its work, refuses to descent when it is called. This is a well-known affliction, perhaps of all artists, but certainly of poets. Thera are some who can command it at will; those who, I think are more full of an abundant poetic energy than carefull for perfection; others who oblige it to come whenever they put pen to paper, but with these the inspiration in either not a hight order or quite inequal in its levels. Again there are some who try to give it a habit of coming by always writing at a same time; Virgil with his nine lines first written, then perfected every morning, Milton with his fifty epic lines a day, are said to have succeeded in regularising their inspiration.
It is, I suppose the same principle which makes Gurus in India prescribe for their disciples a meditation at the same fixed hour every day. It succeeds partially of course, for some entirely, but not for everybody. For myself, when the inspiration did not come with a rush or in a stream, - for then there is no difficulty, - I had only one way, to allow a certain kind of incubation in which a large form of the thing to be done threw itself on the mind and then wait for the white heat in which the entire transcription could rapidly take place. But I think each poet has his own way of working and finds his own issue out of inspiration incertitudes.