Was high school graduation sad or depressing for you?

I'm a senior in highschool I'm becoming depressed at the thought of my inevitable graduation. I have known these kids since like 1st grade and grew up with them for years. I felt like I have been in school forever and kind of thought the carefree life would never end. Now I log on to facebook and everyone's talking about how they got accepted into colleges. Its just weird seeing all these kids growing up and moving on. I'm a hardcore introvert and pretty anti social. Being the shy guy that i am, I wonder how I even made the friends I have now. In a few months I will probably never see them again. Its just really sad for me.