Think about all the times you've forgotten something. Whether it was an essay, your keys, something when you were traveling, we all forget this. Items can easily be replaced, as long as you have a couple bucks in your pocket.
But forgetting items isn't the only things we forget. Remember, for a second, if you've ever forgotten someone (if right now, you're welcome to leave). A lot? That happens.
You're preparing busily for a party. The decorations look great. Check. The food's prepared. Check. You review your guest list once more, and suddenly you realize. You didn't invite your best friend.
Dazed, you now try to make out an invitation and get it to them as quickly as you can. Stressed, you try to prepare, but your friend says she's already made plans. Ashamed and devastated, you move on.
Take a deep breath. Before you go through the hassle of preparing the party, sit down and think about who you want to invite. Think of all the people you hang with, talk to, and work with. And if you're stumped on who to invite, call up a friend and just tell her. It's better to face embarrassment that way then to forget someone.
You don't want to forget anyway. Think of all the times you forgot someone.