You're discounting the case where precisely because it fits the narrative, it is effective.
Getting coffee and building the narrative of "I'm a Hard Worker who will now do his Hard Work with Focus and Determination, look at me getting ready with coffee" is priming yourself for that hard work, the narrative is part of your motivational structure and embellishes your Focus and Determination.
Being too aware of "it's only plain old me, whether in a uniform, or in an office, or at Starbucks" is needlessly sabotaging an often effective placebo-like effect that relies on your internal narrative.
Epistemologically useful, possibly, but contraindicated as an instrumentally useful habit.
And this is why I love LessWrong, folks--sometimes. In other rationality communities--ones that conceived of rationality as something other than "accomplishing goals well"--this kind of post would be hurrah'd.
Our internal dialogues are often exactly that: dialogues that suit a narrative. Narrative building (the basis of the narrative fallacy) is often quite detrimental to attempts to think clearly. It is therefore beneficial to detect and correct for biases introduced from narrative building. But it can be hard to distinguish a 'clear' thought from one that is a consequence of a narrative.
I offer a heuristic to make the distinction between a thought which is a direct attempt to model reality and a thought which is based solely on its suitability to a narrative:
Two examples:
1. When buying something: Often times, when I'm standing in a Starbucks line for a coffee and try to imagine why I'm standing there (when I can make my own coffee both at my home and at my office), I am usually returned with a feeling of being part of The People Who Do Things. Or one of being a Hard Worker who needs his Coffee to do his Hard Work with Focus and Determination. It fits too well while introducing a character in a novel. After I started noticing this, I've been realizing that coffee is not as useful in improving my focus as I thought it was earlier.
2. In conversations: This must be very familiar to most people. Anecdotes get highly embellished based on their suitability to a story. Also the way they are usually 'narrated' rather than just 'conveyed'. Realizing this when it happens can be quite useful.
Other examples?