So that when I’m at work I can instantly go from “professional mode” to “coach mode” in a matter of seconds without needing to go to the locker room.
I wear a t-shirt or polo underneath whatever I’m wearing for the same reason: I can strip down to “coach mode” instantaneously. I suppose I’m like Clark Kent.
But in all seriousness, I do this to eliminate decision fatigue. It turns out that the quality of our decisions gets worse the more of them we have to make. It’s why doctors tend to get diagnoses wrong later in the day, and why judges tend to give harsher sentences later in the day. Their brains are spent from making too many decisions.
It’s why Mark Zuckerberg wears the same t-shirt every day, as Steve Magness describes in Peak Performance:
“At the end of 2014, in Zuckerberg’s first-ever public Q&A session, the question that garnered the most attention was, ‘Why do you wear the same T-shirt every day?’
‘I really want to clear my life to make it so that I have to make as few decisions as possible about anything except how to best serve this community,’ replied Zuckerberg, clarifying that he had ‘multiple same shirts.’ He went on to explain that, when taken together, small decisions–like choosing what to wear–add up and can be quite tiring. ‘I’m in this really lucky position, where I get to wake up every day and help serve more than a billion people. And I feel like I’m not doing my job if I spend any of my energy on things that are silly or frivolous about my life,’ he said.” (p. 142).