I may be stating the obvious on this one. The painfully obvious. But it's so important to me that I feel compelled to make sure you are in the loop too.
It's called a Keepers file, and everybody needs one. You'll know a "keeper" when you see it - it's an email, tweet or otherwise glowing note about you that makes you smile from ear-to-ear. The kind that makes your whole day, week or month. Keepers are like gold nuggets that never lose their value. You'll know it's a Keeper because every time you read it you feel energized, confident and/or appreciated.
Your Keepers deserve a home. They are proof of how hard you've worked, the impact you've had -- or maybe they just make you laugh. I began saving Keepers a few years ago when I started training new hires at Google (thanks to a tip from a more seasoned co-worker). As the emails came in, I would label them "Keepers" and read through the email folder on rainy days when I needed a pick-me-up.
Now I've figured out a better system - every time a Keeper comes in, I copy and paste it into a Google Doc with a note about who it came from. WOW. What a difference the new system has made! Emails were a little tough to sift through - the Google doc is like a Keepers file on a quad-shot latte.
I don't read Keepers to be vain, and I don't re-read them all that often. I read them when I need a reminder about the difference I made in someone else's life, or an accomplishment I am proud of. I read them when I've forgotten that I have so much to be thankful for. I hope you are doing yourself the favor of saving Keepers too.