Being drunk, being sober: which should you be when you're writing?

At an event recently, the poet Rowan Williams was reading some of his favourite poems by other poets, and he was asked what he looks for - hopes for - when he comes to a poem for the first time. For someone who's so clever and so erudite (not the same thing) his answer was wonderfully simple: "I hope to go into a poem sober, and come out a little bit drunk." And I know exactly what he means. I'm not a poet, and I don't read poetry in an organised, professional way. But there are always one or two...