What helped was scribbling a few phrases in my journal as soon as I came in. Those crabbed words led me back to the feelings of that walk. They were the rushed but essential first draft.
It's the perennial problem, letting the words flow enough in the beginning to get you (more or less) where you want to go. Care too little about the final destination and you'll muddle yourself from the start. Care too much and you won't be able to put one syllable in front of the other.
Word processing has made the first draft a rare document indeed. How difficult it is to push forward without using the delete key; to hold in mind the perfect image while valuing the imperfect one that materializes in its place.
In so many ways, a first draft is more precious than the final draft it makes possible: rare, ephemeral, a product of struggle, a product of doubt.