I remember very vividly when I was younger, I walked into the kitchen and said hi to my mom. She turned and said, "Honey, I love you. But you've said hi to me 23 times today, you don't need to every time we're in the same room." 

Ouch.

But I've always remembered that! I've been conflicted ever since.  I feel rude walking into the breakroom and not saying hi to the business manager having lunch, even though I said hi when I first saw her in the morning. But I also feel like it's annoying when someone says hi every time we pass in the hall.

What do you do? How do you acknowledge a person you've seen all day, every day?!