Write down single words, one-liners, anything that takes your interest. This can be either at the time or at the end of each day, or first thing each morning. Whatever time suits you best to gather and interpret your memory of these moments.
The exciting aspect to this is that new insights will arrive each time you sit down to review these notes. A month later even, you will have seen so much more since you originally noted your thoughts that your perspective will have changed, even if the change is minute, there is still a chance that the minute change in your perspective will result in that vital spark, the new catalyst for your next brilliant song.