It drives me crazy when I send someone a work email and then realize I left something out, so I have to send a follow-up email 15 seconds later. It feels like such a sloppy waste of time. On the other hand, I love it when people send me an email and then send me another one 15 seconds later because usually the first one says, and I'm paraphrasing here, "I need you to do a bunch of mundane work please!" And then the follow up says, "Never mind, you did all this mundane work last year and I can reuse it." Getting me that second email offers me a real sense of accomplishment without doing any extra work, which is nice once in a while.