I don't think there is such a thing as tears of joy. It's at least a misnomer! You cry because your sad; even though you have a smile on your face, everything is going great, your reaching your self actualization goals =), you still don't want to leave the people you love. Thanks to everyone who saw me off, bought me drinks, met me in the rain, helped me prepare, took care of my cat, and said see ya soon. You mean the whole crazy, mixed up world to me.
FYI: I like the word misnomer and will name my "pet" rat it, maybe