Train of Thought

There is always a word at the tip of my tongue that, left unvoiced, retains itself passively in my deepest thoughts. It’s difficult to follow my train when it keeps switching tracks. What once led me to Barstow, now to Braintree, and I never look back to think of what I left behind, what could have been. The thought, like me, changing while the pen ink dries, the cigar ash lingering, reminding me where I came from.

What would cause a derailment, perhaps? A loss of sanity? A breakdown in prose?