Hi Sarah,
What you are experiencing is common to almost all poets, writers, play-writers – we all have those moments when words or lines are in our head, but refuse to come together in a cohesive way upon the page. What I have always done is write down the lines as they come – don’t worry about their being a part of a poem – just capture the words, the lines and put them away for another day. Many times, when I have been going through a “dry spell” I jot down the lines that pop into my head and then discover, when I am writing whole poems again, those lines find a place into my poems or, become the inspiration for a poem. If you must judge something – judge the quality of your writing – set standards for your poems – requiring that they possess imagery, meaningful line breaks, rhythm, occasional rhyme, hyperbole – all of the elements that make poetry, poetry. Perhaps you should look at this as a good thing. Writing is a bit like farming – you prepare the ground, you plant your crop, you nurture it, harvest it and then, let the fields go fallow – fertilizing them and enriching them. It is, I think, like that with poetry – a time to harvest and a time to enrich the “soil.” I hope this helps. I think I can guarantee you that the poems are there – waiting to be harvested. Your friend in poetry, Susan