Basically, you're overworked so you're not as focused. One little example I can remember was this - we were maintaining a less than impressive codebase under a

Basically, you're overworked so you're not as focused. One little example I can remember was this - we were maintaining a less than impressive codebase under a lot of time pressure (bad management practices, such is life). There was a bug caused by me using two functions together that looked like a pair, but in fact the function to transform data was not idempotent, and the function to undo that transformation would sometimes mangle the data. I should have tested the code involved instead of just using it naively, but I wasn't in the mental state of mind to watch for such things. Little things like that. Programming takes a lot of mental discipline, so you need to be at your best.