Goodbyes. Why are they so hard?

Why do people say ‘Goodbye’ even when there is nothing good about the bye that they are saying? Maybe saying bye to Leo and Andrea is soo sad and hard for me because I know that this bye really means ‘Bye forever’ not ‘Bye, I will see you later.’ I said goodbye and there was nothing good about saying it.
I will be leaving in like 10 hours or so. . .
Goodbyes are sad,but they are even sadder when you have met someone awesome that you have gotten so close to and you know the goodbye is for good. Like the models, they are so great and I love them but I will never see them again. I hope I do but I doubt it.