I actually understand what you mean. I'm more likely to get worked up and/or misty-eyed over powerful "happy" moments rather than your typical sad stuff. Give me something heroic and amazing and I'm mush. Kill off a character or two, and I hardly bat an eye.
That;s why "You bow to no one" gets me so much.
Heck, think back to the original Transformers movie. I didn't really cry at Optimus death(I came close, though), but what really worked me up was when he showed and just started kicking ass all over the place. That scene, and the accompanying music, inspire me to this day. Heroism. Maybe I secretly wish to be a hero? Or to do heroic things? Don't we all, in a way?