Aww....Moxie, I'm sorry you had to miss out after all. As everyone else has duly noted, you clearly are someone who cares about other people and wants to put them before yourself. First, you wanted to faithfully be at your sister's side during the birth of her first child. Then you selflessly looked after your friend's children while she went to be with her husband during a crisis moment.
You have no reason to be dissapointed in yourself! At the end of the day, you did what you felt was the right thing to do and that meant helping someone out in their time of need.
I don't know what the future holds for you as far as being in a sorority goes, but I hope you will come to appreciate what you have done for others.
.....Kelly
