Marrige

My grandma and grandpa have been married now for 63 years. They were married when my grandma was 18 and my grandpa 20. Now they are in the mid 80's. I know back then it was a different time and I sit here and wonder, how can someone be so committed to someone else at that age. I mean I'm 18 and I have never truly loved someone (other than my family.) Plus the fact that they are able to put up with each other for 63 years?! Every vacation, experience, and every moment spent together. It's almost like they are connected by the hip and can't do anything with out that other person. I don't know how they do it? I spent 3 days with my friends and I didn't go 2 days without getting irritated at least 3 times (plus lack of sleep.)  I guess it's something I will never understand unless it happens to me one day, and even then I will wonder, what is wrong with my emotions? I even sit back and watch my parents once in a while. How they communicate with one another, and how rarely they fight (and when they do it's kinda funny.) I mean I never see them fight, its just every once in a while if their tired or what not, but I don't know I guess in a way it just confuses me.