I stopped drinking coffee because it was making me feel too anxious. I also stopped caring about my total productivity per day for the same reason. Instead I make sure I just do something per day.
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I'm not sure how much it'll be worth, but I stopped worrying about any productivity of any particular day. Instead, I choose to write tools that are placed strategically: server config distribution system, data bus, data storage system, command issuing tool, things like that. I make my colleagues' lives easier (or so I like to think).
Though I'm in a somewhat privileged position, being a half-sysadmin and evading the most repeatable and/or customer-facing work.