I am a very grateful person. Not in a "grateful for my lot in life" sort of way (though I try to be that, too), but in an "I say thank you a LOT" way. I thank people often for small things, I thank people profusely for big things, I find myself signing emails "thanks" even when I'm the one helping the person I'm emailing. My boyfriend has actually told me to stop thanking him for dinner when he takes me out, but that goes against my nature. Just something to do with my personality, I guess.
I recently kind of went out of my way to help someone. Not necessary to get into details, but at some point through the process, I realized that she hadn't said "thank you" at any point. I got fixated on it. I started bitching about it. And I realized that I have a serious issue with needing to be acknowledged/appreciated for things that I do. Which is my shit, not hers.
In my Buddhist practice, we're encouraged, no, expected to help people without expecting gratitude in return. This experience was an important lesson for me, and I'm grateful for it. I don't deserve a medal, and yes, while it's polite to thank someone for helping you, it's not, or at least it certainly shouldn't be, the reason to help someone in the first place.
Lesson learned. And by the way, she did wind up thanking me. Profusely.