A series of conversations recently has had me thinking about the subject of inspiration, and the fact that many writers have a fear, verging on the pathological, that inspiration will 'vanish'.
I put this down to GCSE English (or O Level, if you're old enough). Nearly every student of English literature gets told the story of Coleridge, and the 'man from Porlock' who interrupted him while he was writing Kubla Khan so he 'lost' the inspiration to finish the poem.
I think he just got fed up with it. Why not? We've all got unfinished fragments galore on hard drives and in notebooks, haven't we? So when poor old S.T. was being nagged by his cronies to finish the work, I think he came up with a convenient excuse.
But it's become the stuff of legend, that lost inspiration, and as long as we believe it happened to him, with all his genius, then we're sure it will happen to us.
A good enough idea has one defining criterion - durability. If it slips away from you in the night, then it wasn't good enough to start with. Let it go and find another. Often an idea fades because it needs more time to mature, or to accrete other aspects, like plot or location or voice - if we try to force it, by jamming it down on the page too early, it's like a seedling that's outgrown its strength, all pale and leggy and destined never too bear fruit.
Trust your subconscious. It will give back inspiration when it's ready. Until then, get on with something else and you'll be surprised how vigorous your good idea will be, when it finally emerges.